extra image in material for comp masking ?

[cgdom]

It's been a while since I needed to do this, but is there a workflow in v-ray where I can have an image in my material that gets pushed through to a render element but does not actually show up on the material itself ? Basically I have a bottle with a textured label i want to control sections of in compositing. My plan was to create an extra image that has rgb channels representing the various areas on the label i want to mask out and have some render element pick that texture up. The ugly solution is to do a render layer with a swapped texture on the bottle that represents the mask but that is basically unnecessary render time.

[Dan Andersen]

An 'Extra Tex' render element, using the include/exclude set functionality of that element, should do the trick?