Working with Date Variables(Unit 5)

Visual Basic for Applications

Objectives In this unit, you will learn how to:

Reserve a Date variable

Use an assignment statement to assign a value to a Date variable

Assign the VBA Date, Time, and Now functions to a Date variable

Control the appearance of dates and times using the Format function

Perform calculations using Date variables

Objectives

In this unit, you will learn how to:

Convert a string to a Date data type using the DateValue and TimeValue functions

Refer to the active cell in Excel

Use the Range object’s Offset property in Excel

Preview and print a document in Word

Refer to a control on an Access form

Create a custom toolbar in Access

Concept Lesson:Discussing Date Variables

A Date variable is a variable that can store date and time

information

Reserving a Procedure-level Date Variable When creating a Date variable, datatype is always

the keyword Date

Date variables are automatically initialized to the number 0

The dtm ID indicates that the variable is aDate variable, which can store date andtime information

After using the Dim statement to both reserve and initialize a Date variable, you can use an assignment statement to assign a different value to the variable

Examples of Dim Statements that Reserve Date Variables

Exhibit 5-1: Some examples of Dim statements that reserve Date variables

Using an Assignment Statement

Date literal constant examples: #January 7, 2003#

#12/31/2002#

#11:05:00 AM#

#7:30:07 PM#)

Exhibit 5-2: Some examples of assignment statements

Using VBA’s Date, Time,and Now Functions

VBA’s Date function returns the system date, which is the date maintained by your computer’s internal clock

VBA’s Time function returns the system time, which is the time maintained by your computer’s internal clock

VBA’s Now function returns both the system date and time

AssignDisplayDate Procedure

Exhibit 5-3: The AssignDisplayDate procedure

Message Box Displayed by the AssignDisplayDate Procedure

Exhibit 5-4: The message box displayed by the AssignDisplayDate procedure

Using the Format Function

You can use the VBA Format function to control the appearance of dates and times

The syntax of the Format function:

Format(Expression:=expression, Format:=format)

• expression specifies the number, date, time, or string whose appearance you want to format

• format is the name of a predefined VBA format

Help Screen Showing the VBA Predefined Date/Time Formats

Search for “Format Function” in VBE Help box

Examples of Using Format Function(Try the following examples in the Immediate Window)

dtmTime = #17:04:23# dtmDate = #January 27, 1993#

Print Format(Time, "Long Time") Print Format(dtmTime, "Medium Time") Print Format(#8:30:00 PM#, "Short Time")

Print Format(Date, "Long Date") Print Format(dtmDate, "Medium Date") Print Format(#March 21 2000#, "Short Date")

Print Format(dtmTime, "h:m:s") Print Format(dtmTime, "hh:mm:ss AMPM") Print Format(dtmDate, "dddd, mmm d yyyy")

Print Format(1,"General Date")

Using Dates andTimes in Calculations

VBA provides two functions called DateAdd and DateDiff that you can use to perform calculations involving dates and times

The DateAdd function allows you to add a specified time interval to a date or time, and it returns the new date or time

Using Dates andTimes in Calculations

The DateDiff function allows you to determine the time interval that occurs between two dates

Unlike the DateAdd function, which returns either a future or past date or time, the DateDiff function returns an integer that represents the number of time intervals between two specified dates or times

DateAdd and DateDiff Syntax DateAdd Function

DateAdd(interval, number, date)

DateDiff Function DateDiff(interval, date1, date2[, firstdayofweek[, firstweekofyear]])

Valid Settings forthe Interval Argument

The valid settings for the interval argument

Examples of theDateAdd Function

Exhibit 5-8: Some examples of the DateAdd function

Examples of theDateDiff Function

Exhibit 5-9: Some examples of the DateDiff function

Converting Strings to Date or Time

VBA DateValue function or the TimeValue function converts the string to a date or time, respectively

The syntax of the DateValue function is: DateValue(Date:=stringExpression) stringExpression represents a valid date ranging from January 1,

100 through December 31, 9999

The syntax of the TimeValue function is: TimeValue(Time:=stringExpression)

stringExpression represents a valid time ranging from 0:00:00 (12:00:00 AM) through 23:59:59 (11:59:59 PM)

Examples of Using the DateValue and TimeValue Functions

Exhibit 5-10: Using DateValue and TimeValue functions

Summary Use Date, Time, and Now functions to return system date and

time

Use Format function to control the appearance of date and time

Use DateAdd Function to add a specified time interval to a date or time, and then return the new date or time

Use DateDiff Function to calculate the number of time intervals between two specified dates or times

Use the DateValue function to convert a date string to a Date data type

Use the TimeValue function to convert a time string to a Time data type

Excel Lesson

Open Excel and select Cell A1

Open Object Browser in VBE

Search for ActiveCell object

What does ActiveCell object represent?

Open immediate window and type: Application.ActiveCell.value = 108

Application.workbooks(1).Worksheets(1).range(“C5”).select

Print ActiveCell.address

Why do think active cell is a member of application object?

The Offset Property You can use a Range object’s Offset property to

refer to a cell located a certain number of rows or columns away from the range itself

The syntax of the Offset property is: rangeObject.Offset([rowOffset] [,columnOffset])

rowoffset and columnOffset could be positive or negative

Positive rowOffset refers to rows found below the rangeObject

Positive columnOffset refers to columns to the right of the rangeObject

Illustration of the Offset Property

Exhibit 5-12: An illustration of the Offset property

Select Cell B5 in ExcelTry the following examples in the Immediate window:

• activecell.Offset(-1,-1).Value = "upper left“• activecell.Offset(-1,1).Value = "upper right"• activecell.Offset(1,-1).Value = "lower left“• activecell.Offset(1,1).Value = "lower right”

Excel Lesson:Creating the CalcHours

Macro Procedure

Open Martin’s workbook

View the code template for the CalcHours procedure

Pseudocode for theCalcHours Procedure

Exhibit 5-11: The pseudocode for the CalcHours procedure

Word lessonPrinting a Document

You can use the Document object’s PrintPreview method to preview a document on the screen before printing it

You can use the Document object’s PrintOut method to print the document on the printer

The syntax of the PrintPreview method is:

documentObject.PrintPreview

The syntax of the PrintOut method is:

documentObject.PrintOut, which prints one copy of the entire documentObject

Word Lesson:Using date variables in Word

Open Pat’s document and view the code template for the

PrintInvitation procedure

Pseudocode for the PrintInvitation Procedure

Exhibit 5-13: The pseudocode for the PrintInvitation procedure

Access Lesson:Using date variables in Access

Begin by opening the database and viewing the ProjectsForm form

Then open the Visual Basic Editor and view the code template for the AssignDates procedure

Referring to a Control on a Form

Each of the text boxes on a form is considered a Control object in VBA

Each control belongs to the Form object’s Controls collection

You can use the formObject.Controls(controlName) syntax to refer to a control on a form

controlName should be enclosed in quotation marks

Pseudocode for theAssignDates Procedure

Exhibit 5-14: The pseudocode for the AssignDates proedure