Oh yes, got it. And you want to trigger such a program by assigning it to the special keys using the supplied Logitech application, right? This might lag a bit.
My idea—and what I'm actually using, just with Genius keyboard—was to replace this application with HotkeyP, which has much smaller footprint and is incredibly more versatile. (I don't know this Logitech thing, but I suppose it's terrible to the same extent as the one from Genius.)