Wiring voice control button to aftermarket radio

[xzirri]

Hi again! I recently upgraded my radio to a Kenwood head unit and I'm quite pleased with it. However, I have now learned that answering a call on a touch screen while doing 60 mph isn't the easiest thing to do. After playing around with the steering wheel buttons I discovered that the MODE button can be used to reject calls. Still, I have no idea how to pick up calls with the steering wheel buttons. This got me thinking: some of the facelift steering wheels have a separate voice command button. Is this button wired to the radio loom, or to the car computer loom? Is there an easy way to redirect this button to the radio if it is wired to the car computer?