This will depend on what hardware you are using to send the commands to the stepper motor. NI offers motion controllers and drives that come with all the functions you will need to operate the motors. Depending on the size and number of motors, you will have different hardware requirements. Take a look at the motion products available here: http://sine.ni.com/apps/we/nioc.vp?cid=1506〈=US
If you have more questions, you can always contact NI at www.ni.com/contact to help spec out the system.
If you are using third party products, you will have to call their dll from LabVIEW using a Call Library Node function. This gives you access to all the functions in a dll.
Hope this helps.
Regards-
Julie S.
Applications Engineer
National Instruments
