Search notes:

Excel: Review -> Protect -> Protect Workbook

In some versions of Excel, this Menu is Review -> Changes -> Protect Workbook.
Review -> Protect -> Protect Workbook allows to prevent accidental changes of the
This protection can optionally be enforced with a password.

See also

The menu File -> Info -> Protect Workbook
The methods protect and unprotect of the workbook object.

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