i've found a way to do this with my behringer bcr2000. it's a bit abstruse, but it works.
all midi signals are send to 1st comp by usb. there is midiOX running and sending all signals back to the bcr2000 (still by usb).
in usb-modes 2 and 3 (using midi IO's as midi interface) those signals, which are input for the bcr2000, are send to the midi out, thus i can send them to the 2nd comp. Voila, the signals are send to 2 comps! (And can be used in both.)