A Building That Can Use Items...

Okay i'm making a map and I need a building that can use items. I gave it an inventory, an attack, everything it needs. I made some items that have NO EFFECT WHEN USED. I based them off potions so when the building obtains them, it can use them and they have 1 to 3 charges. They either increase the attack damage or the attack speed. This is done through triggers, so when a building uses an item it gains a PERMANENT damage/attack speed increase, rather than holding an item like Gloves of Haste. I can't get the items to be useable though. Can someone help me?