You will need to rewrite the code so the center of the rectangle is at the 0, 0 point. So the lower left will be two negative numbers (-5*bb, -1.5*bb), the upper right two positive numbers (5*bb, 1.5*bb). I think this is simpler than trying to use the Add2 command to adjust the center.
David Maudlin / Architect
AC 22 - Mac OS