You can just set a session variable for users that don't get charged shipping and then add a condition for you shipping charge to check that value and not charge shipping when it is set.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.