[X-Raym]

use a while loop like

track = reaper.GetSelectedTrack(0,0) -- Get first selected track, you can put that into a track loop too



programNumber = 0 -- First index

retval = true -- Start loop

while retval then

retval, programName = reaper.EnumTrackMIDIProgramNames( track, programNumber, '' )
programNumber = programNumber + 1
if retval then
-- DO WHAT YOU WANT HERE
end

end -- this will stop once there is no value returned

(not tested bu you get the idea)