how to apply maskfield to dragforce in pyro

[koutaku 0]

Hi, I am trying to make my smoke moving slower and slower when it reached the specific area. I try to use a dragforce but it worked everywhere in my sim ,how can i apply maskfield to it  like somthing we can do with popdrag.

or is there anyway to apply  a mask to bouyancy based on temperature or y position?

if somebody can tell me how to do that will be great help,thank you