Arduino controlled bench power supply
@Russell McMahon - Circuit with inverted opAmp worked. At the moment I can't do full test, but with voltage converter (+30 and -7, basically no load only oscilloscope test), values moves full range up and down. I need to set proper resistor values and use proper transformer. But I think it will work anyway. 
And I came to idea to use as reference source digital pots them-self. So simply replace opAmp outputs to digital pots. But this needs to be tested later on. If you'll get other useful links to related topic, please post those as well. 
Thank you. :)