how to construct stepper motor driver?
Is your project the stepper motor driver, or is this for another, larger project? 

Unless you specifically want to learn about the intricacies of driving stepper motors, I would recommend just buying an off-the-shell stepper driver, either in IC form, or completely assembled.

I'm a big fan of the Allegro Micro stepper drivers.

If you want a simple, off-the-shelf solution, spark run offers a couple really inexpensive stepper-driver boards (seriously, they pretty much cost as much as the equivalent parts).



(Images are links)

They would be quite simple to interface with your USB DAQ system too. It would just take two DIO lines. One would set the direction, and the other would cause the motor to step - one step per cycle.