[KMFrog]

well, in theory you should be able to block the "file in the hole!" message getting sent to the clients and replace it with your own...

I must admit I've never seen this done though, so it may not be as easy as that - the sounds may be done client-side... and if that's the case, you wont be able to block them unless you handle (re-write?) the whole grenade throwing event so clients do not detect it as a real grenade throw... and that would be complicated