Hello,
About this instrument driver it would be a good idea to contact Agilent since they are the once who built the driver. Now, I downloaded the driver and went to the setpwrm parameter subVI. Those values can be changed in LabVIEW by creating a constant to their inputs or controls. I believe you have done that, so probably you are missing one thing. This subVI has a note that it says that in order to have the changes applied you need to have no value applied to the instrument and the Force Transaction VI must be switched off.
I hope this helps.
Best regards,
Ricardo S.
National Instruments.