I would recommend you take a look at some of the free remote control software programs on the market. The purpose of this type of software is to give you access to a computer as if you were sitting in front of it, even if you were not even in the same geogrpahical location.
Good site: http://logmein.com for the LogMeIn Free product.
Typical scenario:
- Laptop is sitting, connected to the projector, in the front of the room. Laptop has the LogMeIn Free demon running on it.
- Controlling PC is remoted into the Laptop via LogMeIn, and is in full screen mode. Controlling PC is essentially acting like the laptop.
Presenter can then control the laptop via the PC w/o issue.