To prevent others from unhiding hidden sheets, inserting new sheets, renaming sheets, copying sheets, or deleting sheets, protect the workbook’s structure:

1. Choose Review ➪ Changes ➪ Protect Workbook.
2. In the Protect Workbook dialog box, click the Structure option.
3. (Optional) Provide a password.

After performing these steps, several commands will no longer be available when you right-click a sheet tab: Insert, Delete Sheet, Rename Sheet, Move or Copy Sheet, Tab Color, Hide Sheet, and Unhide Sheet. Be aware, however, that this is a very weak security measure. Cracking Excel’s protection features is relatively easy.

You can also make a sheet “very hidden.” A sheet that is very hidden doesn’t appear in the Unhide dialog box. To make a sheet very hidden:

1. Activate the worksheet.
2. Choose Developer ➪ Controls ➪ Properties. The Properties dialog box, shown in the following figure, appears. (If the Developer tab isn’t available, you can turn it on using the Customize Ribbon tab of the Excel Options dialog box.)
3. In the Properties box, select the visible option and choose 2 - xlSheetVeryHidden.

After performing these steps, the worksheet is hidden and doesn’t appear in the Unhide dialog box.

Attention..!!

Be careful! After you make a sheet very hidden, you can’t use the Properties box to unhide it because you aren’t able to select the sheet! To unhide such a sheet, press Alt+F11 to activate the Visual Basic Editor. Locate the workbook in the Projects window and select the name of the sheet that is very hidden. Press F4 to display the Properties box, in which you can change the Visible property back to –1 - xlSheetVisible.