canceling acknowledgements

list Larry Barber
Fri, 22 Oct 2010 16:18:55 -0500
Message-Id: <AANLkTikhQ6NkY6A-nH=user-2a7e5b9319ef@xymon.invalid>

Is there some way to cancel an 'ack' after it has been issued?

Thanks,
Larry Barber