Authentication Credentials Server

The site is configured for anonymous access. One area is configured with basic authentication. When the user clicks on a menu item they will request an .asp file in
the anonymous part of the site that will redirect or trasfer them to the secured part. Along with this request I would like to pass the necessary username and password.

Using:

Response.Redirect(http://username:password@website/asp/index.asp)

doesnt work as the credentials are lost

Using:

Server.transfer doesnt work either.