Midi note length / mute groups

[pparish]

Is there a way to tweak the length of a midi note? OR to set up mute groups? I've had no luck w/ the Sibelius manual, but I'm sure there's a way. My problem stems from notating drum parts and getting the midi playback to reproduce what was written -- namely getting the open hi hat to behave and 'close' when the closed hi hat note is played. Or, getting midi to play functional cymbal chokes or any other slice of 'staccato tricks with midi' ... I'm sure someone has had this same issue ... thanks in advance!

p.e.