[chirp_users] Blocking Transmit on Selected Channels

Greetings,

I am programming some radios for auxiliary volunteers with our local fire department. We wish to provide them the ability to monitor the county sheriff repeater, but to not be able to transmit to it. After poking around the best I could come up with was to set Duplex=split and Offset=0.00000. Is there a preferred method?

Thanks, Jim