William

The regexMatch pattern won't help at all.  You also can't solve your problem with just a url rewriter, because all of the internal links in the site are generated by the friendly url provider.  So, what you need is both a friendly url provider to generate societe, plus a url rewriter to interpret societe.  You also need a module to 301 redirect any old société.aspx links from other sites and search engine indexes to the new societe.aspx.

As far as I am aware the Url Master module is the only one around that does all this for you.

The latest version is not in beta, it's ready for release and my (and a few other sites) are already running it.  I hope to have the new version released before the end of this week, I'm just waiting on a couple of things.  You can wait until I post it on my site for download, or you can email me now and get a version.  If you're installing it onto a live site you'll also need a trial licence, which you can get from http://www.ifinity.com.au/Licensing/

-Bruce