I have the dubious privilege of replacing a set of spreadsheets with
shiny new ones based on a shiny new back-end database. So far so good.

At some point in the near future we'll replace these intermediate-stage
workbooks with a new reporting system.

The problem is probably familiar: we know there are "downstream" user
spreadsheets that reference these outputs, but we don't know how many
or where they are - some may be business-critical; we can't turn off
the intermediate stage until we've dealt with all the downstream links.
Well, we could (the old "turn it off and see who screams" tactic) but
we'd rather not if we can avoid it.

Some apps can be identified by adding logging code to the
Workbook_Open/Auto_Open macro(s). But what about worksheets that
contain explicit external links that won't cause the workbook to be
opened in the "normal" sense at all? Is there any way to record that
activity? It would be enough in the first instance to know the sheet
was being referenced.

Possible? Impossible? Wild-card search all *.xls files across the file
servers? (Maybe not so crazy an idea at that)?

TIA,

Mike