Fixed end but variable start (and duration)

[meileetan]

I have an activity that must end by a certain date. Start date depends on the completion of a few tasks and it can start as soon as one of these dependent tasks end. To illustrate:
Dependent task 1 ends Jan 1
Dependent task 2 ends Feb 1
Variable task must end by April 30. It can start as early as Jan 1 (i.e. when Dependent Task 1 ends) but if Dependent task 1 gets delayed to March 1, then this Variable task can start on Feb 1 (i.e. when Dependent Task 2 ends).

To further complicate matters, the duration of Variable task must be at least 5 days, i.e. cannot start later than April 30-5d.

How can I best reflect this in MS Project?

[JulieS]

I'm afraid there isn't a direct way to accomplish all of the needs.
You can set a deadline on the Variable task.
You can set a Start No Later Than constraint on the variable task.

You can make the variable task a successor of the Jan tasks however a F to S relationship is always the later of the two. So if the first task moves to past Feb 1, you'll need to manually remove the link to the Jan task and re-link to the Feb 1 task.

[meileetan]

Thanks Julie. How do I set a "start no later than" constraint on the variable task? I've already set a "end no later than" constraint = 30 April. Or were you saying I can do only one of the 2, not both?

[JulieS]

You cannot set two constraints on a single task. Use a deadline for the finish date and the SNET constraint.