Apple TV & Airplay - can I lock signal?

I just installed Apple TV in all 5 conference rooms in my office and people can now connect to the projector over our wireless network. The only problem is that anyone can take over from the presenter by using Airplay (or AirParrot) to take over the Apple TV for that projector. Is there a way to 'own' or 'lock' the Apple TV session so it can't be 'stolen?'