Can anyone recommend a simple board that takes a USB signal (will be from Mach3 on Windows 7) and puts out a 0-10V analog signal?

More context: I was helping someone get one of those ebay 6040Z CNC machines setup and getting the spindle speed controllable by Mach 3 has been a nightmare. Followed many unofficial tutorials we found, but there's nothing official from the manufacturer, and it's just not worth the time to chase this down anymore. I did get the spindle speed controllable by a potentiometer that puts out 0-10V, so most reasonable solution at this point would be to just get an independent board to generate the 0-10V signal. And I'm assuming that setting up a second USB controller in Mach 3 would be easyish.

Thanks.