Good question. I believe that I was wrong earlier when I said that 20752 was working as master code (which I think is a layman's way of saying "the IR protocol"). So, you're right, changing the function numbers wouldn't really accomplish anything. The Vizio user's guide says that the universal remote code (for 5-digit remotes) is 31517. However, the Comcast remote doesn't seem to accept this code when I try to assign it to the AUX device (when you assign a device code, two red light blinks mean success; one blink means failure. I always get the one long blink).