Did you check all of the commands in device mode? If it's not there can you learn it from the OEM remote? Once you have the command in the harmony and know how it works, re-run the activity setup and at the end choose the "yes, but I want to add more control" option. There you will be able to send that command at the beginning of the activity and then send another command(s) to undo it at the end of the activity.