[Zope] form Image Object

Hi, Is it possible to keep an image object over http requests? (without a core session tracker) eg I've a form which allows the user to upload an image. Before it is all the data and image is stored the user gets a preview of the data and image. When he then pushes the 'Ok' button, the image and data should be stored. The problem is that at that moment I don't have a fileobject anymore... how can I keep my fileobject? Thanks in advance, Tom