[Spell] Neutral Building Spell

[Dancyspartan]

Hi. I'm currently trying to create a neutral tower that exists on the map from the get go. If you approach this building you can press a spell. This spell will make the buyer the new owner of the building, and I'd actually like for the building to "forget" the spell after the purchase has been made.

I've made some attempts creating a custom spell, and using triggers to make this happen but no luck so far. All help is appreciated.

Much thanks in advance.