I have a similar question - this thread seems to be the closest. Here's my scenario:
I have a Publisher Task that is scheduled to run every hour and another task that is triggered by the first task. The 2nd task's duration varies and can sometimes take longer than an hour. The 2nd task loads from a QVD file that is created by the 1st task. When the next hour comes around the 1st task is triggered again, but will fail if the 2nd task has not yet completed. It fails because the 2nd task is basically "holding" onto the same QVD file that the 1st task is trying to store into. We seem to run into what amounts to file sharing violations pretty frequently.
Anyway, when the next hour comes around and the 1st task is triggered again, is there a way for it to check and see that the 2nd task has not yet completed and in that case, just hold off until the next hour?