I have a couple of thoughts on this...

I am assuming the momentary switch for your garage door opener operates on low voltage (12 or 24 volts). If that is the case, I'm not certain, but I don't believe you can mix the 12V and 120V in the same box per NEC rules.

An easy way to do this would be to get a door bell switch and connect it to the garage door opener wire through a small hole in the wall next to your switch. It might not look as nice, but it's functional.

-Jeff