RewriteRule /doc(.*)\.htm /XMLProcess.asp\?xml=$1.xml
Now to access documents use URL like http://www.mysite.com/doc/somedir/somedoc.htm. Search engines will never know that physically there is no somedoc.htm file and content is dynamically generated.How cool is that?
Later I learned that you can achieve the same effect by creating a customized 404.asp. Options = Good.