Do not attempt this unless you are an experienced coder.
To create a combat Medic you would need to combine elements of
both the Barney combat code and the Scientist heal code. I can't
even begin to list the things you need to impliment a brand new
class like that.
Barney and Scientist entities are derived from the CTalkMonster
base class, all I can recommend is that you study the talkmonster.cpp,
barney.cpp and scientist.cpp SDK files long an hard until you
understand exactly how the AI works before you even try to attempt this.