There are many ways to control a stepper motor from labview, but you need a hardware stepper motor controller to communicate with from labview. The controllers vary greatly depending on the application, could you post more details, ie motor type, resolution speed needed, type of application etc... I have done a few applications which controlled a steppers in the past, where labview served as the motion control and interface to a stepper motor system.
See the problem is, you need something to output the pulse train.
Right now I'm using LabVIEW to write an acceptance test for a stepper
motor, but I'm using a Galil servo/stepper PCI card in the computer,
connected to an Anaheim Automation stepper driver, which outputs the
LabVIEW can generate a pulse train, but it has to be able to tell some
piece of harware to actually output that signal. As falkpl was
saying, you can use LabVIEW as the interface to something like a
stepper driver, but you need the hardware to do the work of outputting
the highs and lows.
I have an Applied Motion Driver (3540i) which I used to use to drive the stepper motor through a program called SI Programmer, although that program has limited options for control. I figured that labview alone could act as the driver, giving me more options. I guess I need to have labview "talk" to the driver in some way to control the stepper motor.
Two ways I had controlled stepper motors in the past is:
1. The cheaper method: I used a pontech stp100 stepper driver (>$100)- this is a serial communication stepper motion controller, you can send the serial commands to program the motor and communicate with it through labview and VISA.
2. I controlled many motors from compumotor with their own motor drivers which took a pulse train (each pulse caused a step of the motor) and controlled the steps from a 6602 counter/timer card and labview to provide the logic and user interface to the motors (there was feedback and sensors involved with this project).
Neither was very difficult and both were developed with labview 5.0 and 6.1 so I know you can do control with the software you already have.