If I want the mod wheel or the foot pedal of my SL-88 key to control Expression (or any midi controller data), how do I set that up within Cakewalk/Giga 160?

I can get my Ztar Z-10 to do it because the Z-10 allows me to assign the joystick or volume knob to control any midi controller data I want to send.

Is it a matter of the controller having the ability and since the SL-88 doesn\'t feature this, i can\'t do it? Or is it possible to get the SL-88 to send expression messages by tweaking cakewalk or giga?