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VBA program units: Subroutines and Functions

Subs:

•a chunk of VBA code that can be executed by running

it from Excel, from the VBE, or by being “called” by

another VBA subprogram

•may have zero-to-several arguments that provide

for values to be input to or output from the Sub

•can be created with the macro recorder or typed

in from scratch

Sub name (optional arguments)

End Sub 2

•functions can return values

•a VBA subprogram that can be executed by using its name

in a VBA expression or an Excel formula

Functions:

•functions cannot be recorded, but must be typed into the VBE

•functions may have zero-to-several input arguments

Function name (optional arguments)

End Function

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Examples:

Function Twice(mynumber)

Twice = 2*mynumber

End Function

Sub hello()

MsgBox ("Hello") „ MsgBox “Hello” would work here

too

End Sub

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Examples:

Function Icy(temp)

If (temp <= 32) Then MsgBox ("Yes")

Icy = temp

End Function

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When you write VBA code, it is possible to “get away” without

declaring the data types of variables that you use.

But, this is bad programming practice, so it is best to declare

the “types” of all variables used in VBA:

Dim <variable-name> As <type>

This requirement is enforced by putting the Option Explicit

statement at the top of every VBA module you develop.

“Declaring” variables

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Making VBA work

Save As Macro-Enabled workbook (.xlsm)

Make sure Options -> Trust Settings is allowing macros

Make a new directory for each VBA/Excel workbook (clarity)

Functions: test by calling in Excel worksheet (or from Sub)

Allowed to return values

Multiple arguments possible

Subs: test by running with F8 in VBE

Allowed to change cells

Multiple arguments possible

Check settings by loading Kick Calculator; should run!

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Enforcing variable declaration

put Option Explicit statement at the top of every module

or

set VBE‟s Tools Options

Require Variable Declaration

and VBE will do it for you!

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Object-oriented programming

Objects : entities that have attributes (“properties”) that can

be manipulated

These are generally organized

in hierarchies:

Microsoft Office

Word

Excel

“Application” Objects

in red

Selection

The object

that

corresponds

to cell A1

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Object Collections

Workbooks all currently-open workbook objects

Charts all charts contained in a particular workbook

Worksheets all sheets contained in a particular workbook

Referring to objects in a collection

Worksheets(“Main”)

Charts(“XY”)

Complete object references

Application.Workbooks(“Project6”).Worksheets(“Main”).Range(“B16”)

Can be simplified when unambiguous

Workbooks(“Project6”).Worksheets(“Main”).Range(“B16”)

Worksheets(“Main”).Range(“B16”)

Range(“B16”)

Workbook

Worksheet

Chart

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Object-oriented Programming & Variable “Scope”…

X

X

Y Y

Z

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The “SCOPE” of a variable

How far is the “reach” of the variable, or

from where can the variable be “seen”?

1) only within a single procedure (Sub or Function)

such a variable is generally called a “local” variable

variable is declared using a Dim statement

within the procedure

2) only within the current module a “module” variable

declared using a Dim statement before the first

Sub or Function in the module

3) everywhere, in all procedures, in all modules open

declared using a Public statement at the module level 12

Module 1 Module 2

Dim k As Integer Public R As Single

One

Dolt

Two

Howdy

Current

Workbook/

VBA

project

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Where can k be referenced?

a) Everywhere in Module 1

b) Everywhere in Module 2

c) Anywhere not in Function Dolt

d) Only in Sub howdy

e) Everywhere

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Where can R be referenced?

a) Only Module 1

b) Only Module 2

c) Only Function Dolt

d) Only Sub howdy

e) Everywhere

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Where can y be referenced?

a) Only Module 1

b) Function Two and Function Dolt

c) Only Function Two

d) Only Sub Howdy

e) Everywhere

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Where can j be referenced?

a) Only Module 1

b) Only Module 2

c) Only Sub Howdy

d) Only Function Two

e) Everywhere

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Static & Constant

Static y as Single

Static is used, instead of Dim, when you want the variable

to retain its value after the procedure is finished…i.e., if

you want the variable to have the same value the next time

the procedure is run.

Symbolic constants can be used to store values with names,

where the values should never change. Use the Const keyword

for this:

Const Rgas As Single = 8314.3

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How to invoke Excel spreadsheet functions from VBA:

Application.WorksheetFunction.function-name (arguments)

Example: creating a function RangeArray

uses Min and Max functions in

Excel, not available in VBA

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UserForms

1) Design it

2) Set up code that processes what the user types into the

boxes & clicks on the radio buttons

3) Hook that code to the “Compute Re” button

4) Set up code that quits & hook it to the “Quit” button

5) Set up a way to bring up the form 22

UserForms

Insert a UserForm in the Visual Basic Editor (VBE)

Toolbox

contains

stuff to

put on

form

New &

empty

form

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Properties

The Properties window

(in the bottom left corner

of the VBE) lists

properties of the selected

object – here, the

userform.

Use it to set those

properties…

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Setting up the name and caption:

A user form is a variable and needs a

name (like any variable).

The Name is how you will refer to

the form.

The Caption is a property of the

form – what the user sees in the top

of the form:

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Add title and field for density

Properties window

now refers to the

label object

Change caption:

You don‟t need to change the Name since we‟re not going

to be modifying the label in our program. The Caption is

what‟s displayed on the User Form. 26

Add textbox for value

It‟s essential to name the textbox since that value will be taken

from the user and used in the program.

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Add a “frame” to contain the units choices:

• Frames used to group similar objects.

• Exclusive OR

• Must be large enough to include all of the

choices you want to provide.

• Feel free to remove the caption for

aesthetic reasons (just remove the text in here)

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Add an option button in the frame for one units choice

“stretch” button so

caption shows:

change title

& caption:

Again, option buttons MUST be named as that name will be

used in your code.

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Change default button value to true:

add button for alternate

units with caption and

default false:

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Add similar entries for pipe diameter,

velocity and viscosity:

Easiest way: just copy each row and change the

names and captions in the corresponding

Properties window.

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Add a command button to compute the answer:

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Change command button name, caption & font:

The name of the command

button is the name of the VBA

subroutine that performs the

calculation

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Add a Quit button with similar formatting…

The name of that button is also used in your program.

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The UserForm is now complete, but two important

features are missing:

1) there is no way for the UserForm to appear for use

2) when the Compute and Quit buttons are clicked,

nothing will happen because there is no VBA code

behind them

Hooking things up

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Double-click the Compute Re button.

This will cause the following Sub wrapper to

pop up in a code module:

In here, we must add code

to carry out the necessary

calculations and display the

Reynolds Number result

Hooking VBA code to the “Compute Re” button…

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Filling in that code:

• convert units, as required

• compute the Reynolds Number

• display the result

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This variable is

the name you

created for your

textbox

This is a variable

you create and

use in your

calculation.

Do NOT use the textbox name on the LHS of

your calculation – it will not work!! 38

What is the variable that VBA uses to return

whatever the user types here?

a) Diam

b) PipeDiameter

c) Pipe Diameter

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What variable does this Sub use in its

calculations for this?

a) Diam

b) PipeDiameter

c) Pipe Diameter 40

What is the variable that VBA uses to return

whatever the user types here?

a) mu

b) viscosity

c) fluid viscosity

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How to run and remove user forms

insert a new module and add this Sub to start the UserForm

double-click the Quit button and add the code to remove

(“unload”) the UserForm

run the StartReynoldsNumber macro…

…and enter

values

with units

selected

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UserForms

UserForms can be loaded automatically when the workbook

is opened. (This is called an “event handler.”) And they can also

be unloaded automatically when the workbook is closed.

1. Go to VBE and double click on thisworkbook item in Project

Explorer. (If Project Explorer doesn‟t show up, use view)

2. Change left field at top from General to Workbook.

3. Type in ReynoldsNumber.Show

(this is not on any exam; it‟s just a useful FYI)

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Things to Remember!!!

• Create your own variables to carry out calculations, NOT the variables in the user form

• Make sure the variables from the user form that you assign to your created variables are the same names as in your user form

• These variables are those used from your text boxes and your option buttons, NOT your labels

• You should not have the same name for your text box as for your label

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This variable is the

name you created

for your option

button

FormatNumber – number of digits after

the decimal point. Does not round.

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If you get a Reynolds number of 2134.3721 and the

program says MsgBox(FormatNumber(Re,1)), what

will the message box say?

a) 2134

b) 2135

c) 2134.3

d) 2134.37

e) 2134.4

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MsgBox Function

MsgBox(“prompt”,buttons,”title”,helpfile,context)

optional

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MsgBox Function

MsgBox(“prompt”,buttons,”title”,helpfile,context)

optional

Button codes

vbOKOnly vbExclamation

vbOKCancel vbInformation

vbAbortRetryIgnore vbDefaultButton1

vbYesNoCancel vbDefaultButton2

vbYesNo vbDefaultButton3

vbRetryCancel vbDefaultButton4

vbCritical vbSystemModal

vbQuestion

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MsgBox Function

Putting line breaks into the message displayed:

MsgBox result is button clicked by user