I would set up the BC In as both Track and Remote.
If Live sends the BC a PC message, as long as it is on a different channel to the BC setting, the BC will ignore it. If it is a problem change the BC's Midi channel.
If this still doesn't fix you problem you can always use MidiOx and MidiYoke to filter out the returned PC messages.
If you are still in trouble let me know exactly what you are trying to do.
All the best
Royce