Making a spreadsheet very hidden

Using the Hide command you can hide the data and formulas from "inquisitive minds". But some of them still can use Unhide command. Nevertheless you can completely hide Excel spreadsheet so that it will be needed some VBA programming to unhide it.
Hide in the popup menu:

Hide spreadsheet in Excel 2016

But anybody can unhide it easily: by right-clicking in any spreadsheet and selecting Unhide in the popup menu:

Unhide spreadsheet in Excel 2016

To make an Excel sheet very hidden (it wouldn't be visible in Unhide menu), do the following:

    1.    Right-click in the spreadsheet and choose Veiw Code in the popup menu:

View Code spreadsheet in Excel 2016

    2.    In the Microsoft Visual Basic dialog box:

  • In the top Project - VBA Project box, you can see all workbook's sheets (choose another sheet if it is necessary):
    VBA Project Properties in Excel 2016
  • In the bottom Properties - sheet name box, select the Visible option, and choose 2 - xlSheetVeryHidden:
    spreadsheet Properties in Excel 2016

After performing these steps, the spreadsheet will be hidden, and it will not appear in the Unhide dialog box.

To unhide a very hidden sheet, you can use the View code menu and select 1 - xlSheetVisible for the Visible option in the Properties box.