Dog Trainer Using the Web Cam

My dog is not suppose to go upstairs and only sneaks up there to do naughty things like drink out of the kids toilet and tear diapers apart.  I've tried to catch him but he knows his actions are naughty and never goes up when anyone is home.  I figured out a way to scare him into not going upstairs, I'll use my iChat and leave my lappy at the top of the stairs, then everyone has to leave and I'll call my lappy from another computer and "watch" for the little bugger when he makes his move.  What I need is one of those really annoying horns they use at basketball games that I can connect to my computer via USB and then activate it when I see him coming up the stairs.  Or better yet I need a computer program that uses the camera to recognize my dog and set the horn off if he gets close to the computer.