Open Files properties form?

オフライン
I've created a relationship between an itemtype and files. I added custom attributes in the relationship to extend the standard file attributes. When I double click on the file in the relationship grid it opens by default. How do I change this behavior to instead open a form to view/edit attributes associated with the file? Haven't been able to create a view or frm anywhere relevant, and for File Item Type I get the msg: have insufficient permissions to perform ‘update’ operation...