LV does not regulate current (or voltage or any other physical parameter) directly. It can send data to external devices such as your analog output device to be converted to a voltage or current.
For what you are trying to do you would need an amplifier which can boost the ao output to the voltage and current levels needed by the motor. you wish to regulate current and not voltage, then the amplifier needs to be able to operate in current regulating mode.
Since you do not seem to have much knowledge of motors and electronic circuit design, you will probably have a lot of trouble trying to get this working. I am a consultng engineer who has designed circuits for 40 years. I could design a microstepping driver, but it would be cheaper for me to buy one than to spend my time working out all the details.
Lynn
