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?