[Question] Moxie but for HP Help

Hey. Im trying to add an ability that acts like moxie but for hp. Anyone know how to do it? (19.1). I I copy and paste moxie but change attack to "HP". I get a nomethoderror. Thanks.

Pretty sure HP doesn't just follow the same formula as the other stats. There aren't HP boosting moves or abilities in the series to begin with, so changing it to either Def. or Sp. Def. (or both but I guess that'd be OP) sounds more plausible.