Qlab can send MIDI to Max/MSP and easily control anything you'd want. I've also had success with Qlab and Logic's Mainstage, and by far the best option, MIO console controlling the internal Mixer in at MH 2882.
To accomplish this you just need ot figure out what MIDI can be mapped to the control you'd like to change, have Max/MSP, or Mainstage listen to the IAC bus (OSX's inter application MIDI routing option), and have Qlab send to it.
I hope that helps a little.
Charles Coes
cco...@gmail.com www.charlescoes.com"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." - Buckminster Fuller