isight auto white balance

Hi, I'm in the midst of building a patch where a portion of it utilises the isight webcam on board the Macbook Pro to read brightness/light levels (not using the ambient light sensor).

The path is as such: jit.qt.grab to jit.3m

As many of you guys might have known, apple does not provide the feature of disabling auto white balance in the operating system (there is a paid app out there, but I hope to be able to figure it out on Jitter). Even if I adjust the saturation, brightness and contrast level to minimise the fluctuating effect, the auto white balance will still kick in and thereby creating an unstable reading of the brightness level output. I require a stable and smooth reading as I will be using the values for musical purposes.

I am using a simple hand gesture where the hand moves towards and away infront of the isight webcam (imagine mimicking a theremin performance). I've even tried turning the signal into greyscale and using a black glove!

Does anyone know of any ways to get about fixing this? Or would someone be kind enough to recommend something else?