hi what is your hardware setup for sending midi in to the computer...? I've used 2 controllers with one midi input before, just by plugging the second controller, via midi cable, into the first's "midi in"..,,this one, though, needs an out port which also handles "thru" simultaneously
you'll find that some midi knobs may have the same controller assignment as others so you can't use them for a separate function... time for some random emoticons:

well they don't drag and drop onto the page so forget it!