A bit late for the party, I know. But if anyone is still looking for a solution, here it is: On the 'Play' button you can add this script to the 'onValue' session. It will fire the stop button whenever it's own value is '0'. if (value == 0) { send('127.0.0.1:5000', '/stop', 1) } Where '127.0.0.1:5000' = your ip and port of Reaper interface. Now, if you want it to react just like the original Play button from the transport bar, you add this code: if (value == 0) { send('127.0.0.1:5000', '/stop', 1) send('127.0.0.1:5000', '/play', 1) }