NI 408X Ajust

Hello,

i'm trying to ajust the NI-4081 DMM following the Calibration Manual. It still fails at the calling of

niDMM_CalAdjustMisc Function with Setting to NIDMM_EXTCAL_MISCCAL_VREF_DC_VOLTAGE.

 I previously done the same for the NI-4071 and everyting worked like a charm. but the Setting type  was NIDMM_EXTCAL_MISCCAL_VREF

So my question is:  is there a fundamental difference between these two Parameters? I could  find some Information here  about    the NIDMM_EXTCAL_MISCCAL_VREF  but still nothing about the other one. Could somebody helps me please.

Best Regard