[screen_name]

First off you need to "Be more specific.." as Wan said.

Give us some details, like the ways you have tried it, what exactly isn't it doing, etc. Read below...

"I'm trying to make this NPC that does this, but it's not doing it. Any help?"
Doesn't help does it?


EDIT: How are you taking the HP away from the tree?


Do you have a messenger of some sort?