Checking a Player's Health

Is there a way to find the health of an entity or player using what is provided in hammer?
I am working on an infirmary in my latest map and plan on using a logic compare to allow a trigger_hurt with a negative value (for healing players) to only heal players who are below a certain health level.

Edit: Negative trigger_hurt isnt working, I swear that Ive done this before, gah.

This would be easily accomplished with Lua