Using Pro Tools 9 as a Sound Module for the MPC

O.k., so I've got an MPC2500 and am trying to sequence on it using the VST's from Pro Tools 9. I can trigger the sounds in Pro Tools, but what I can't do is get each instrument to react on a different MIDI channel of the MPC. (i.e. MPC channel 1A triggers BOOM, MPC channel 2A triggers Akoustik Piano, MPC channel 3A triggers Battery 3 and so on).

I used to do this with an MPC4000 and a Digi 002 with Pro Tools 7, but now with PT 9 I can't get it to work.

Any help would be appreciatted!