I know I'm able to duck a channel with another channel but I was hoping I could duck a buss with another buss. What I want to do is to group all direct microphone (podium, lav, hand held, and program audio) as direct sources. Then group the room microphones on the ceiling. The direct buss would duck the room buss. So when there is not direct signal from someone talking or playing PC audio the room mics would open up to be heard. Not on/off but a 20db or so bump and duck. So far I'm coming up short. Still learning the mixer a bit though.