Stream only when "on air"?

I am operating a small non-profit radio-station which is transmitting a few hours each week on a FM transmitter which is shared with another radio provider who is transmitting 24/7, i am achieving this by "cutting" into their broadcast. I have a setup with a remote icecast2 server which uses the parallel port and a relay-card to switch audio source on the transmitter when an audio-stream on a pre-defined mount-point starts on the server, and then feed the same stream to the same transmitter. When the stream stops it switches back to the original source after a short delay. When i am broadcasting live, i use "internet DJ console", but i don't have a system for automated broadcast of recorded programs yet...
Airtime seems to have everything i need if i can get it to stream "only" when my scheduled programs starts, and stop the stream when there is
"nothing scheduled". is this possible?