Combine Coinciding Results.

Hello!
I wonder if it is possible to do the following with the help of the formulas alone. I have a list of events which START and END at different times. Some of them start when the other events are still in progress (their end date has not been reached yet). I need a way to combine the results of the events whose times overlap. The results of the overlapping events should be multiplied and stored as a single event. Any help will be hugely appreciated!
Thanks a lot!)
Dima