While I don't think a script like this exists, I can tell you how to pull this off.
1. Make a copy of the script destroy.fpi for the character that you need to protect and rename it something like "protectthischaracter.fpi".
2. Using FPI Editpad (or similar scripting program), add a line at the beginning of the script that says:
:state=0:globalvar=99,setvar=99
3. In a custom script named "customscript.fpi" (or whatever you want to name it) add a line similar to this:
:state=x,globalvar=99,varequal=99:plrsubhealth=1000
In the above code, x is the state you are in (more than likely 0), and the plrsubhealth amount is the amount of health that the player can have at maximum.
4. Place the above created custom script in a trigger zone.
5. Place the custom script from steps 1 and 2 as the destroy script of the character you need to help.
Not that hard, huh?
Priest of the Church of Joe Wood
In memory of Nanee. 9/1/1993 - 5/16/2009. Rest in Peace, little girl.