I have a ceiling mounted projector at my place of work that I need to connect to. It already has a usb cable run through the ceiling to a media control center. It currently uses a pc to run the projector but I would like to use my MacBook to connect. I already have the dvi to vga adapter but how can I change from vga to usb? Perhaps there is a different adapter I can purchase? Thanks for any insight you technologically gifted people send my way.