how do I make an oversized button with a usb cable act as one of the buttons on my keyboard?

what Id like to do is have an oversized button on my desk that will act as the f12 button on my pc. its the button that blender uses to render images. I can make the button no problem, but how do I get it to "tell" my pc that it is an f12 button?

If you want it completely separate, finding a "clicky" keyboard might help. In a clicky keybaord, every key is a button soldered in place. You can open it up, and cut it down to just the f12 key. You'd probably need a ps2->USB adapter, since I don't think these keyboards and USB perts we manufactured for more than one or two years simultaneously. Another option (with your clicky) is just to adopt it, drill out the side, and run leads to the contacts fr f12. If your using a modern keyboard, it will be rather difficult to get into the printed circuitry. Go to a second hand store, find a keyboard that is clicking more than the usual click of the plastic, (probably from windows 98 or 95) open it up, it should be nice and easy to solder new contacts to. (Where am atleast) these keybaords are an abundance, and cost only a few dollars.