When my cats are doing something I don't want them to do I usually say a firm no and clap my hands and the sound startles them and they run off. My mom has 3 cats and every year when they put up their christmas tree they all love to try and climb it and have even knocked the whole thing over once or twice. She got a spray bottle and filled it with water and keeps it by her and when one starts to climb she will spray them with it and they jump off and run away. If it got too bad where it is non stop and you can't sleep maybe you could close the door and keep him out that way.