I shall publically admit my weakness for text-based programming. However, I believe that you're not finding what you're looking for because functions are analogous to VIs and attributes are analogous to properties. So in your case, try using the attribute "NIDCPOWER_ATTR_VOLTAGE_LEVEL" OR "NIDCPOWER_ATTR_CURRENT_LEVEL".
I'm crossing my fingers. Let everyone know how that works out for you, and if you need more help I'll try to get it.
Mark E.
Precision DC Product Support Engineer
National Instruments