LTPowerPlay negative VOUT_COMMAND

To Whom It May Concern,

Part of my design incorporates an LTC2977 PMBus manager where one DAC outputs feeds the SET node (nominally -5V) of LT3090, a negative voltage regulator. I would like to servo the DAC to maintain/margin the SET node at or near -5V. I'm confused how to assign register values in LTPowerPlay for negative VOUT_COMMAND, as I have not seen much documentation on this front. 

Any help is much appreciated.

Warm regards,