I have an Excel 2003 spreadsheet that I am editing with Excel 2007. I am not
the original author of the spreadsheet. I notice that the spreadsheet is
supposed to have two linked files. I have installed the Ultimate Add-In (from
www.dom-and-lis.co.uk) and used it to generate a Links Report.

The report has three sections:
- Linked Files
- Linked Names
- Linked Formulae

According to the report, it appears that one of the linked files, "Book1",
is used in a couple of linked formulae. The other linked file "Book2",
however, does not seem to be actually used anywhere, aside from being linked.

How can I be sure if "Book2" is, in fact, not used at all?