I have both an computer and conventional radio. Can I use two channels to do one function in both radios or only the computer?

Thanks as usual

Are you talking about twin elevator servos on different channels or something else?

Another way is using a mix into a single servo. Is that what you are trying to do?

Thanks for responding. I don't want to use a Y harness on my ailerons.

Okay, in that instance you are going to need a computer radio that does twin aileron servo (or flaperon) mixing. At least I don't know of any conventional radios that do twin aileron servo mixing.