I need help!

Cole is driving me crazy! Well, not really, but kinda. Sorry if I'm really bad, but I leave my computer on nearly all day and sometimes I forget to turn it off at night. Recently Cole thinks he needs to come and screw everything up on my computer! I leave it on because I do many things on the computer and it's nice to have it on when I need to quickly look on the net or when I get a spare minute to work on the computer. It's just convenient to have it on all the time. I have no way of locking this room so Cole can't get in, and it's been really annoying today to turn off the computer just to have to turn it back on again 2 minutes later. I'm trying to not let it get to me. I stress about stupid stuff, this really isn't a big deal, right? I just wish I had a computer desk that locked or something. I don't want to move my computer out of this room, I like where it's at. Just wish I could get him to stay out of this room. Our piano is right next to the door, so when I try to latch the top of the door locked, he climbs up and unlocks it. It's an old house so the door doesn't actually lock. Any suggestions?