Edit / Save fixed file

Hi All

Just wondered if there was a way of tweaking the source to allow the user  to edit and save a fixed html file. I need to edit several files but do not want the user to be able to save it under different names, or open other files.

So I may have a series of html files that need editing at different times, and they may be in different folders. I want to set up a single editor page which i can activate and give a file path to and that will be all the user can do - anyone done this before at all?