below is from Dan who has the following scenario:
I have three programming tasks with three successor testing tasks as described
P1 > T1
P2 > T2
P3 > T3
I want to have one task to define the test environment that starts 14 days
before THE FIRST programming task is completed.
contradicts a well-known best practice of never assigning dependencies to or
from summary tasks. But then, as I've found there are exceptions to most rules. To summarize you want a predecessor against the earliest
completion of a set of three tasks. To
accomplish this you group the successor tasks under a summary task. Then place the test environment as a predecessor
with a 14 day lead on the summary. The result will schedule the Define test environment task to start 14 days before the earliest task completes. The
figure below shows the solution.