Controller of Unit

Hello,
Hopefully someone can help me figure out something that should be obvious...
I have triggers for specific players.
I have two teams.
When someone on a team drops I give shared control of their hero to their team.

My problem is that my player specific triggers won't work for the Allied Controller of the Unit which is still owned by the dropped player.

I want to set a player variable to the controller of the unit. (not the owner) How can I do this?

Example:
Player4 trigger that shows a menu to player4 when a hero owned by Player4 enters a region.

I want to change that into a menu that shows to the controller of the unit that enters the region rather than the owner.

I had a player variable for each player which I was going to set to the "Controlller of entering Unit" but I can't figure out how to do it.

Any help would be greatly appreciated. Using GUI.

hmm i dont know about this one. if you just gave control to one person. like the next player. so if player 1 leaves 2 gets his player. and when 1 and 2 have left 3 gets all of thier units. then its possible but thats not how you want it so :\