On my motorhome I have a sliding window just behind the drivers door,and I need to be able to fit an addtional lock to this, last weeek a breakdown company had to break in because all my keys was stolen, he just leverd the window, poked a through a wire and pulled the handle on the sliding window, and then it opened,he then put his hand around to the drivers door and pulled the tab up on top of the door and all the doors then unlocked, so i want to fit an aditional lock, problem is the sliding track and window are on the outside ! has anyone go any idea's