One problem with our Excel implementation of the CPM method is that the maximum and minimum formulas for the earliest start time and the latest finish times have to be tailored to the specific AON network.

That is, we can’t enter formulas for a typical activity and then copy them down for the other activities.

However, there is a clever way of doing this if you are willing to use some advanced Excel functions.7 This method is illustrated in the file Project Scheduling Ragsdale.xlsx for the LAN project from Example 15.1. The text box in this file explains a few things about the new formulas, including the fact that they deliberately create circular references.

a. Use online help to learn exactly what the formulas for the earliest start times and latest finish times are doing and why one formula fits all for each. Then explain in words how they work.

b. Implement this method for the project in Figure 15.27. You can make up any durations for the activities.