oscMax & mod rewrite

I have an oscmax website and need to be able to set mod rewrite for information pages. Each page has an extra field called "url" which should be used to change the URL of the pages. Example Actual URL: [login to view URL] url field: /about_us/who_we_are/ rewritten url: [login to view URL] In the admin, the "url" field should auto suggest the URL to use based on the page name and its parent pages.