I'll post a link and the process found on gamedesign.net just out of laziness:
Switchable lights
Let's say we wan't a light to be turned on or off by some other event (be it a button, trigger, etc..) What we need to do in this case, is to set up the triggering event (in this case, a func_button) and give it a "target" (we'll use "lt1".) Now, we need to create a light, and give it a "targetname" of "lt1". We now have a light that turns off when we hit the button. If you would like the light to turn on when you hit the button, set the start_off spawnflag for the light.
http://www.gamedesign.net/node/27Note: yootz, please be aware your light will need to be an entity. If you want the button to be shootable to turn off/on the lights that can be done, or you can make it so people touch it (bump into it). I'm sure you can do a small test map to make it work. If you truly need help making it work I certainly will help, just don't have the time at the moment to make a sample map of it. MegaKudos to gamedesign.net