Its written in python (http://www.python.org) and generates a side-by-side comparison of any two files in a web browser.
Sorry its not in pro-iv, but its easier to use someone else's diff module than to code my own.
To use it, print out the function documentation with a windows client, and save to a text file (ie c:\temp\old.txt, c:\temp\new.txt)
Then run htmldiff.py c:\temp\old.txt c:\temp\new.txt, and it will generate a comparison file, and open a web browser.
Mike