Rogerio,
I'd recommend that you take a look at some our example programs which will probably give you some direction in your program. The gist of what you're after is to sample the analog feedback from your stepper motor and send those samples to a waveform graph in LabVIEW. Go to http://zone.ni.com/devzone/devzone.nsf/webcategories/71657AD7D28D90E1862567AF0068761A and check out some of the links from that page.
Best of luck,
Jim Laudie
Applications Engineer, National Instruments