One problem with our Excel implementation of the CPM method is that the maximum and minimum…

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, you 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.8 This method is illustrated in the file P15_39.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.

Example 15.1

CREATING AN OFFICE LAN

An insurance company has decided to construct a local area network (LAN) in one of its large offices so that its employees can share printers, files, and other conveniences. The project consists of 15 activities, labeled A through O, as listed in Table 15.2. This table indicates the immediate predecessors and immediate successors of each activity, along with each activity’s expected duration. (At this point these durations are assumed known.) Note that activity A is the only activity that can start right away, and activity O is the last activity to be completed. This table implies the AON network in Figure 15.2. The company wants to know how long the project will take to complete, and it also wants to know which activities are on the critical path.

Objective To develop a spreadsheet model of the LAN project so that we can calculate the time required to complete the project and identify the critical activities.

Figure 15.27