URL Rewrite

It is our understanding that rewriting URLs happens on the server side so neither users nor search engines are aware of it. However, if done improperly duplicate content can really harm SEO. We wish to avoid that. We are adding some new content to our Classic ASP website. This content is a list (a directory) of links that dynamically create the pages that would occur if a customer did certain searches in our search box and the top of the page. However, we want the URL to be similar to as shown below. We want the URL Rewrite to only be used for these links and never for the rest of the website which is already well indexed, crawled etc... by the search engines. We want the rewrite on the directory links only. [login to view URL] When linked from certain page to read [login to view URL]