I don't have a MIDI keyboard setup at the moment. It's really a question about the origins of the MIDI data isn't it.
If it was coming from an external keyboard you could select the same MIDI channel as the I put for each VSTi couldn't you.
Why not route the midi you want to use out to a keyboard and take a thru or output back from the keyboard and use that as your trigger. Any delay from the original midi is irrelevant as its the midi coming in to Sonar that will drive your VSTi.
Anyone game to try it and see if it works.