How to rescue units from a building?

[Kabel]

I assume this needs to be done via triggers too hard for me to master. So I once again turn to the good old hiveworkshop.


On my map there are neutral buildings. If a player in a specific allied team (player group Terran team) moves one of his units near the building a civilian unit will spawn and permanently belong to that player. It shall only happen once per building AND only to the first player who reaches the building.

So if player B is the first person to reach a building, a civilan spawns that permanently belongs to player B.

(Note: The Zerg players can NOT move units close to the buildings to get the unit inside.)

Imagine a Marine rescuing the people inside the building. Once they come out, the building is empty.

How can this be done in such a simple way as possible?

 

[Dr Super Good]

Give each terran unit a behaviour that performs an area search every 5 or so seconds which looks for buildings with a certain behaviour. This behaviour the buildings have represents rescuable civilians. If such a building is found it removes 1 charge and spawns a civilian unit (using the effect to create units).