Por que você simplesmente não usa o recurso de controle de alterações embutido no Microsoft Excel?
How change tracking works
Change tracking is available only in shared workbooks. In fact, when you turn on change tracking, the workbook automatically becomes a shared workbook. Although a shared workbook is typically stored in a location where other users can access it, you can also track changes in a local copy of a shared workbook.
When changes are made in the shared workbook, you can view the change history directly on the worksheet or on a separate history worksheet. Either way, you can instantly review the details of each change. For example, you can see who made the change, what type of change was made, when it was made, what cells were affected, and what data was added or deleted.