You'd have to turn those off, along with the rest of the OS use of them,
while you are in front, and then turn them back on when you are brought to
the front again. You can't prevent screen clicks, which are handled inside
the OS long before it even cares what application was clicked, if any, from
happening in just your application. If you don't want to do that at a
granular level, just set the volume to 0 when you start and set it back to
its original level when some other application pops up or when you exit. Of
course, the user can always manually turn the sounds back up, but it's
usually a bad idea to undo what he wants to do. If you're worried about
that, you'll have to turn off the sounds for those operations (and hope he
doesn't manually go turn them back on again, of course).
Paul T.