Specific Hitboxes

In darkrp I want to make it so when the player is shot in a specific area a function is run.
Eg He Is Shot In The Groin And Falls Over Or Something Similar.
Where would i put this function in also?

**[Gamemode.ScalePlayerDamage

http://wiki.garrysmod.com/favicon.ico](wiki.garrysmod.com/?title=Gamemode.ScalePlayerDamage)**

and