or a little bit easier does your router have mac address filtering, and if so enable it, and set it to allow only the present mac addresses on the router, (make sure hes not on the router at the time) it works 100% i like it because i share a connection on a college campus, that we have to pay for and i give out the wpa password to the people that i allow on my networ. some of them thought they would try and out smart me by handing out the password to other people and they couldnt get on. heheh its very fun