Detecting player casting a spell from neutral building

How to detect, by conditions, which player is casting a spell from a neutral building ?

You can't

You theoretically could if all your spells were triggered,
and all spells on neutral building are dummy spells based on charge gold.

Of course, my spells are triggered, spell on the neutral building are custom spell and not based on gold. So i can do it "theoretically" ?

Do you use both limber and gold in your map or only one resource?

Use items. Make them free, longish cooldown and when someone buys an item from the building search for the owner of the bought item and.

Hum nice idea, i'll try something with this... the spells targeting a point... Humm i will need to add a dummy buyer because i wanted make a spell so the player can cast it when he is very far from the shop.

give the shop a large range?