the request to modify the calculation depending on the selection is probably better handled by a Parameter than a Filter. Is your real data small enough and static enough that a static parameter type value could be used?
If not - then maybe switching between three views using a parameter where the sales calc is unique to each view. The Parameter would be set to something like Select by Region, Select by Segment, and Select by both.
Create a View (Sheet) Selector for Your Dashboard describes this potential sort of solution.