Edit Hidden Item in List

I’m using SharePoint 2007 and I’m trying to figure out a way to hide a group of fields from being options in a new-item form when a list item is being created by an end-user. However, I also want to make those hidden items available to be edited by an administrator at a later time. Let me be a bit more specific:

1. I have a list of items, some of which are required/optional and some of which are hidden.
2. I want a visitor to my site to be able to make a new item by filling in a form where only the required/optional fields are visible.
3. I then, as an administrator with full control, want to be able to go back after this item is uploaded and add values to the other hidden fields.

I am open to hearing out other methods of doing this if anyone has suggestions. Unforunately, implementing anything through code isn’t an option as my employer has standard SharePoint templates so I’m not allowed to implement anything through code that isn’t available from the GUI interface.