Google for "acme hadess", acme is a program for multimedia keys, maybe that will work. It's a gnome2 app, just install it and then it'll integrate with the control panel.
Word of warning, it will also point an entirely pointless icon in your notification tray. We shout at hadess lots for this braindamage, and he says he'll get rid of it soon, but so far hasn't. So to use it, you'll have this pointless icon on screen at all time. Sucks, but shout at him as well and maybe he'll get the picture