It sounds like the controls you used previously may have been a
    VXM-1-1 where you had motors 1 and 3
    If you do not need to move simultaneously you could use a VXM-3
    (Basically the same setup with 2 Vxm's bussed together controlled by
    1 serial port but now you would have motors 1,2, and 3)
    
    If you need them to move simultaneously then it gets a bit more
    difficult and needs more than 1 serial port.
    
    Cliff