That suggests the problem is as much as anything to do with the file contents, not the format. What you seem to need is something that ensure the files are opened, saved, closed & re-opened before any editing is done. That may not be not something that could be automated and, if it could, would affect the opening process for every Excel file, regardless of the format.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]