Thanks to you, Mathieu, Mike, Hans-Cristoph, I've got it working now. The second hurdle is to send this data out over Midi as NRPN/Sysex messages. Before I re-invent this wheel, is there something already included in pd-extended that would make it easier? I found something on http://www.noisybox.net for sending NRPN messages, but to be honest, I couldn't understand how to use it, it's way too complicated for me.
The purpose is to develop a patch (as an abstraction) to control the setup of an Akai EWI USB wind controller (to select fingering system, Midi channel, etc.). Is anyone on this list using one of these controllers? If you're interested in helping test it, let me know. If I can get it working and you think it might be useful, I'm going to upload it as open source somewhere (not sure where, yet).
Thanks.