Rikki, if I remember correctly (and it's the one you are talking about), it was the Midisport by MOTU. I think you could physically control which channel got "thru'd" and which didn't.
It was a good box too, don't think they make it anymore, but maybe if the OP visits the MOTU website he might find some hardware they make no that would help with his MIDI issues.
They have some good gear.
Then again there may be others too, that allow MIDI manipulation without a PC.
Dennis