Thank you for the information. You gave me an idea. I searched the
emacs source for compare-windows and found it defined in compare-w.el.
I then searched the net for compare-w.el, and found a new version at
http://www.koders.com/lisp/fid38FFF1549CE6B51544A8900E4130B96E65461450.a
spx. I saved that code into a new compare-w.el in my site-init folder
(so I'd still have the original remaining in my lisp folder just in case
there were problems), and voila! It works! Thanks for inspiring my
solution, even if you didn't actually suggest it. :-)