This came up today at the office... convenient timing. As Trever pointed
out, tasks become critical when Total Float <= (stated number of days,
usually 0).
As such, Project has no real way to determine a "path" comprising a 1st,
2nd, 3rd tier critical path. 0 slack is 0 slack, the critical path is just a
listing of the tasks with Total Slack less than a specfiied value
(Tools/Options/Calculation tab).
The example is this. Consider working the schedule as a backward pass from
the end date. You will trace only tasks with 0 (or less) total slack.
Eventually you will come to a branch where both the predecessors are on the
critical path. So pick one at random. You trace that back and run into the
same situation. See how it is impossible for project to dertermine which is
the 1st path and which is the second?
You might consider assigning priorities to the tasks on the critical path.
You can sort or filter on that priority and that would establish paths for
you. Other than that, it is all in the math.
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Jim Aksel, MVP
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