Seems to me the Attachment Tab is indeed a rather special TAB.  So just for fun I tried to drag a formula onto the Paperclip Tab.  It created a formula on a new TAB automatically.

What I was hoping for of course was to actually create a formula on the attachment/paperclip TAB.  Does anyone know if this can be done?

If a way could be found it would definately allow a rather unique feature in TAB since one can add attachements with all sorts of other detail.