unlink asset on assignment

Hi Everyone, I was wondering if anyone had a way either through a rule or possibly a feature enhancement that I can unlink an asset when it is assigned to a student. We use device lockers in our buildings as swap devices when a student breaks a device. We assign that device to the student and refill the lockers on the back end. Currently we link the computers to the locker so that we can see at any one point what is in the lockers. The problem is right now we have to manually unlink the asset when we assign it or it does not show that it has left the locker. Any thoughts would be greatly appreciated.