This will require quite a bit of custom coding to accomplish. it is not a system that is natively supported by eCart. We could help you implementing this through a premiere support appointment:
http://www.webassist.com/premier_request.php
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.