Hi, Csaba911
Looking at your info, Your interface board will only turn on & off your spindle by adding a solid state or larger relay to your Aux 1 output.
Your Proxon mill has a var resistor, I think controlling a power transistor for speed control, Don't think you'll be able to change direction though.
There are several boards that will control the speed by simulating the var resistor and use Mach's PWM output.
Can't think of the Mfg. at the moment, Some one will probally jump in about it.
Hope this Helps, Chip