I've been told that this can't be done.
lolwhat. Who told you that nonsense?
Make sure your remote is addressed to your tv set and it should work. If its not working its really due to one of three reasons.
1.The input button itself is broken.
2. The remote might have it locked out, call in to the call center and have them teach you how to unlock it. Some techs lock the remotes at the first installation to hopefully prevent customers calling in with snowy/blue/black screens.
3. Very rarely sometimes the code doesnt take completely and not all the functions interface very well. You can try different remote codes to see if it works.