stepper motor control through RS-485 serial communication

I need to run several stepper motors simultaneously through MATLAB. I need to randomize rotational rate, cruise time (the time between direction changes) and directional change. I was searching for a code online as a starting point for me. I found one of the codes available through the link below:

http://www.mathworks.com/matlabcentral/fileexchange/16439-stepper-motor-control-with-gui

My stepper motors are integrated stepper motors with the driver and encoder. They will need an RS-485 serial interface for PC communication. In the code, there is written:

    inout=digitalio('parallel','LPT1');

I guess this will not work for me. Is it possible if anybody helps me to modify this for a serial port communication type motors and further suggestions will be more than welcome.

Thank you in advance