when you talk about form, are you talking about a page that edit a content object stored in the database ?, (i.e: a contact form, article, or any user defined content class )
Case yes, you can achive it by overriding edit template for the offending class (i.e: objects of a custom guestbook class ) then adding tpl code to list your objects
To see how to list your objects simply copy ezp full view folder template and change it to your needs
To got it you will need to know how to override an ezp template, and understand ezp template language
Problem is that there is no examples how to merge edit and full view templates.
I do know, how to get node id for new item.
Edit form contains variables: $object.id, $edit_version, $edit_language, $main_node_id How to get those values?
