Okay, on a map I'm making, i want to use a system where either one of the two players controls portions of the map. When a unit is in an enemy region and all the enemy units are dead, the region changes control to the unit's. The problem is, is that I've used a trigger which changes control of the region when there are 0 units in that region controled by the region's owner. But it seams that when you kill a unit, it stays counted as a unit as long as it decays. So even though I have defeated every unit in the region, the game still thinks there are about 16 units controled by that player.
How would I alter this system so that the region changes control after a certain condiction is met? | 
