Never had that problem with dd because she was to short to reach! DS however is a tall chunky monkey and delights in turning off the TV/cable box, especially when dd is watching her programme. Mind you I don't mind if they watch less TV but...
In the initial stages I tried to distract him with other things like stacking tower etc.
Next step was I just gave him a quick tap on the hand accompanied by a firm no don't do xyz and sat him in a corner in the room and walked off. No success.
ATM it's same procedure but actually putting him in his room with door open. We get a few complaining/accusing moans and that's it. Guess what... still no effect and he still pushes the buttons.
What next? Shut the door on him? That would feel a bit cruel.
Have to add, that of course dd (4) does push the buttons as she changes channels etc. so obviously ds thinks it's o.k. to do it...
Any advice and pearls of wisdom welcome.