Hi,
I asssume you are using the GPIB-232CT-A in S mode, to act as the controller. Some version of the GPIB driver supported the GPIB-232CT-A directly. Check
here.
If not, the
User manual has the serial commands you can use in S mode to control the GPIB-232CT-A.
Finally, I know some MACs use RS422 ports. Make sure you have a RS-232 port.
DiegoF
National Instruments.