Link Tasks with Conditional Predessors

[Doug]

How does one accomplish the following:

Task E has conditional links to predessor tasks. For example:

Task E starts upon the earlier completion of either Task A or B.
or
Task E start upon the later completion of either Task C or D
in additon
some of Tasks A - D may have conditional links to other tasks.

 

[davegb]

How does one accomplish the following:

Task E has conditional links to predessor tasks. For example:

Task E starts upon the earlier completion of either Task A or B.
or
Task E start upon the later completion of either Task C or D
in additon
some of Tasks A - D may have conditional links to other tasks.

Project doesn't have any built-in capacity for conditional
dependencies. It uses the Critical Path Method model, which does not
provide for such a thing. I guess you might be able to jury rig
something using VBA, if you have the skills available.

Hope this helps in your world.

 

[Bob]

Beyond what's possible in custom code, there is not a feature like this in
Project.

 

[Steve House [MVP]]

Slight amplification on the other responses. Your second example is
precisely how links normally function in MSP - Tasks C & D are both linked
FS to task E. The link sets the earliest date the task is allowed to start.
Both C & D must finish for E to start, thus E will start after the last of C
or D is done. However the first situation, starting on the earlier
finishing of A or B, is indeed not possible in Project. Frankly, I don't
see how such an arrangment of 5 tasks could ever actually occur, simply
because there is one and only one possible start date for E. So A finishes
on day 5, B finishes on day 15, C finishes on day 10, and D finishes on day
20. What single date satisfys the requirement of "on the earlier of 5 or 15
AND on the later of 10 or 20?" In basic logic, for an AND condition to be
true, both of the terms on either side of the operator must be true - there
is no single date here where both "5 or 15" and "10 or 20" are
simultaneously true. You'd need to have the task starting on both day 5 and
day 20, obviously impossible because it only can start once.