is this possible?

can I use an m-audio sp2 sustain pedal in an akai mpd's expression pedal IN to sustain the notes when I hit the pad, with garageband? or is there a way to do this automatically without the use of external devices? everytime I hit the pads, it plays as long as I hold down pad. if I let go it stops. What I'm looking for is a way for the sounds to keep playing after I let go of the pad.