By using the MIDIOutputEventInBytes, you can send arbitrary MIDI messages to the MIDI output. Here is a Sound that should do the trick. It sends two bytes with the channel number as part of the first byte and the program number as the second byte (as per http://www.midi.org/techspecs/midimessages.php)
-- CarlaScaletti - 16 Oct 2009
I figured it might require using that prototype and typing in some binary MIDI code. When I get home and take a look at your sound, I may decide to create a dedicated prototype, since I may be needing to do this a lot.
-- MarkPhillips - 16 Oct 2009