It must not be stored in the Session. You can use the "set session value" server behavior on the upload page to save a session variable explicitly so that it will be available later in the process.
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.