Add "H" as follows

AudioBus Value = Bus M,A,B,H Value,Input
AudioBusOff Value = Bus M,A,B,H Value,Input
AudioBusOn Value = Bus M,A,B,H Value,Input


Just as various inputs at times need to be added to or removed from the Master, A, or B buses, they also may need to be added to or removed from the Headphone "bus."