Units get in way of building

in warcraft3, when you build something, but an enemy is in the way, You cant build there.... but if u build something, and an ally with shared control is in the way, you CAN build there

how to make so i CANT where my ally that gave me control is?

replies are greatly appreciated

Use a generic point order event and check if the issued orderid equals a building id (you might want to use the IdInteger2IdString Jass-vault function to make this task easier)
If yes, use GroupEnumUnitsInRangeOfLoc with a filter that only allows units of the ally to get all units in the way into a group variable.

If the unit group is not empty -> cancel the command by issuing a "stop" order to the triggering unit.

The proposed solution requires some JASS knowledge.