DirectionsCritPath.XLS: Project Planning by the Critical Path MethodVersion 3.12 10/27/2007John O. McClainJohnson Graduate School of ManagementCornell UniversityIthaca NY 14853This is a very simple program, intended for teaching purposes. You are welcome to use it in any manner, and change it as you see fit. This model comes without any guarantee whatsoever, and is distributed free of charge. The calculations are done by a Macro. Before running the macro, first enter the data on a new worksheet according to the instructions below. Then run the macro using the following menu options:Excel 2003: Tools, Macro, Macros, CPM, RunExcel 2007: View Tab, Macros, CPM, RunNote: If the macro does not appear, or does not work, or if you get a message to the effect that "the macros have been disabled", you need to "Enable Macros". For instructions, click on the link below:Help with macro securityINPUT Data: Enter the data on any sheet as follows (see the Example sheet):The top row is for titles.Column A must have activity names. A title for this column should appear at the top.Column B must have activity times (durations). The time units do not matter, but must be the same for all activities.Column C and subsequent columns must contain the predecessor activities, one predecessor per cell. Be careful that the name of the predecessors are exactly the same as the names you used in the first column.MODEL: The CPM calculations of Earliest Start (ES), Earliest Finish (EF), Latest Start (LS), Latest Finish (LF) and Slack (sometimes called Float) will appear on the sheet on which the data reside.The model also produces input cells, in which you may put both a start time for the project and a deadline for project completion.DIAGRAM: A Gantt Chart is produced, showing the activities starting at their Earliest Start times. Each activity is represented by a bar with length proportional to its duration. However, the predecessor relationships, usually shown as arrows in a CPM diagram, are not included. Instead, each activity's label, on the left of the chart, includes a list of all of its Successor activities.COMPATIBILITY WITH @RISK: The CPM Macro puts formulas into the Excel Spreadsheet rather than just numbers. Therefore, after running the macro, you may use @RISK to simulate uncertain activity times.To do this requires that you have @RISK installed on your computer.Replace the Activity times with @RISK Distribution Functions such as =RiskUniform(1,3).Indicate as Output any cells for which you want a report. I suggest the cells containing Earliest Project Completion Time and all of the Slack values.The @RISK simulation will then tell you the mean project completion time, along with a range of completion times that happened in the simulation. You may also view a histogram.@RISK will report the same statistics for the Slack values. The histogram for a slack will tell you what percentage of the time a given activity had Slack=0, and hence was on the critical path.

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ExampleActivitiesTimePredecessorsSample CPM Problem. To calculate a solution,A2With Excel 2003, use Tools, Macro, Macros, CPM, Run.B4With Excel 2007, select View Tab, then Macros, CPM, Run.C3ADD5BE3CAF5CBG2EFC0Project Start TimePage Down to see the Project Gantt Chart19Project Deadline19Earliest Project Completion Time0Slack for Project Completion TimeActivitiesSequenceESEFLSLFSlackSuccessor ActivitiesA-->C,E102797CEB-->D,F204040DFC-->E,F,G49129120EFGD-->C349490CE-->G5121514172GF-->G6121712170GG7171917190

Example

TasksSlackTasks and their SuccessorsGantt Chart with Activities at ES Times

WarningWARNING: YOU NEED TO ENABLE THE MACROS IN THIS FILETry these steps. If step 1 does not work, then go to step 2.STEP 1: Try to enable the macros For Excel 2007,A.If you see the Security Warning in your menu bar, proceed with step B.If the Security Warning is not there, go to STEP 2.B.In the Security Warning, Click Options.C.In the Alert Window that appears, click Enable This Content and click OK. For Excel 2003,A.Close this file. Then open it again.B.In the window that appears, click Enable Macros.If a window like this onedoes NOT appear, then go to STEP 2.STEP 2: If Step 1 does not workIf you DID NOT get a Security Message, then your security setting is too high.Here is what you should do: For Excel 2007,A.Click the Microsoft Office Button at the top-left of the screen:B.Click Excel Options.C.Click Trust Center, then Trust Center Settings, and then Macro Settings.D.Click Disable all macros with notificationE.Exit from Excel. Closing the file is not enough. On the menu bar, select File, and then Exit.F.Open this file again and follow the instructions in STEP 1 to enable the macros. For Excel 2003,A.On the menu bar at the top of this page, select Tools, then Macro, then Security.B.On the Security Level tab, select Medium and click OK.C.Then exit from Excel. Closing the file is not enough. On the menu bar, select File, and then Exit.D.Open this file again and follow the instructions in STEP 1 to enable the macros.

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