Backwards critical path for secondary task path?

Question

I’m using Project 2010, and can’t seem to get Project to do what I want to see.

I have a primary task path, call it tasks A, B, C, D. I have another secondary task path, call it tasks 1, 2, 3, 4. Task 4 is a predecessor for task D; however, I do NOT want task 4 to drive the start date of task D. I can manually schedule the secondary task 4 so that it ends at the start date of task D, but then should the start date of task D change due to its primary automatically scheduled task path (A, B, C, D), I would have to manually change task 4 to match the new start date of task D. (This would be acceptable if there were just one or two dependencies like this, but I have more like 50).

Another way to say it is that I want to automatically plan the secondary task path BACKWARDS from an event in the primary task path. (I don’t care if the start of the secondary task path is driven backwards to a date before the current date or project start date. In fact, that’s one of the things I want to see).

Essentially, I am looking for a BACKWARDS flowing critical path from a specific event. Is there any way to do this? (I have played with the constraints, but without much success).

Answer 1

Use a Start-Finish constraint on task 4 with task D. If task D is pushed out because task C is slipping, then the start date of task 4 should also slip. I do not think that starting task 4 late will push out task C with this type of constraint.

Answer 2

I think you might want a FF relationship with task D always finishing after task 4. But can start whenever task C finishes. For 8 tasks of a notional 3 day duration you would have...

The "extra" 2 day duration for task D combined with the "+2days" on the FF relationship reflects how much of task D cannot be done until task 4 completes.

Sorry if I misunderstood your need.