Take a look at this example program:
How to Control the Inhibit Out Line to Disable Power Drives
http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B45EACE3F08F56A4E034080020E74861&p_node=DZ52469&p_source=External
Here is more information on the Inhibit Outputs:
http://digital.ni.com/public.nsf/websearch/0B2217C7F1293E17862569E70001267E
Hope this helps-
Julie S
Applications Engineer
National Instruments