Need to Create Mobile Website Version of Website with ASP CMS

We have a website that uses an ASP-based CMS. We are not sure if the CMS is licensed or open-source. We would like to create a mobile version of this website. Content editors will need to be able to use the ASP CMS to update both the original website (this functionality already exists) and to update the mobile version of the website (this is the functionality you would create). We want to give the content editors the option of specifying content just for the mobile version of the website. I am thinking that each page in the backend editor could have fields that allow the content editors to enter text and images just for the mobile version of that page. That way, the mobile user is served a simpler version of the page. Alternatively, the backend user could maybe click a box that allows the mobile version of the page to be automatically generated from the original website content. If there is a better way to handle this problem, please feel free to give your suggestions. Please note that it will NOT be sufficient to create a set of stylesheets that automatically degrade the original site's content for the mobile website. Many of the mobile website pages will need to have customized, simpler content. We will share the URL of the site with qualified bidders.