You need to separate this into two different parts: hardware and software. You first need to determine what kind of hardware you need. You said you "believe that this can be controlled by the voltage". Are you sure? What does the documentation say? If it's controlled by a voltage level, what are the specs? This will help to determine what kind of hardware you need to buy and/or make.
The software part is the other half. This really isn't all that difficult, but the exact implementation depends on a lot of factors. One of these is whether you get a DAQ device from NI, or you get one from another vendor, or you build your own. I think you should spec out your hardware first. If you need help with this part of it you can provide more information and we can suggest a couple of items, or you can look over the products that NI sells, or you can call your local NI sales rep.
