You need a backend language like PHP to do it. You can either learn PHP and do it yourself, find someone else's script and plug it in, or buy a software package using PHP or some other backend language. My guess is you'll want the latter so Google around till you find something.
Check to see if you have Perl (or php, Phyton, Ruby, etc.), then do a routine (daily?) chron update and done. Sitemap made. Next biggie is how often do the SE's hit your site, and which files they hit routinely.