CanI programmatically set PXI 8431 ports to half duplex (two wire)?

Hi,

I'm using a PXI-8431/8 RS485 card for half duplex comms. I am using the usual VISA serial port setup for baud rate, etc, but I also want to set the port mode to two wire, no handshake.

At present I can do this from Windows, using the device manager, but it depends on somebody knowing and remembering to do it. I want to automate it so that it is always set in my initialisation, regardless of who has used it do do what. 

Can anyone suggest how I can achieve this?

Thanks

Malcolm