One way to do this is to isolate the things that can change regularly
like the year number and build the filenames and headings up from
that. If you only have to make a single change of year number then
the scope for parts getting out of sync is much reduced.

Why can't you just send them a corrected version?

Or a patch file to alter just the latest differences (old school
method from the days when updates had to go down a dialup modem).

You can use VBA in one project to alter the code in another or to add
code to a newly created workbook but you would need to test it very
carefully to make sure it does exactly what you want.

This is precisely why I recommend converting the project to an addin
and using a template workbook for subsequent years. Both are, as you
would well know, easily maintainable for updates/revisions over time!

--
Garry

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