Just got my new MADI card .... delighted!

I am using a Behringer BFC2000 to send simple controller messages to control the output levels. This works great as I can assign a single slider on the Behringer to the first output slider of a linked pair of outputs on totalmix. This allows one slider to control a stereo pair of outputs.
I would like the faders on the Behringer to respond to moving the faders in totalmix as well, but it seems that no midi is sent. Is this true .... can I hack Mackie mode to customise scenarios ..... has anyone any clever suggestions ?

Thanks