Hi Chris!
Hide the sheet
Tools > Protection > Protect Workbook
Give and confirm a password
You'll see now that the Format > Sheet menu has hide and unhide grayed
out.
But be aware that this is not a very secure form of protection and
that the passwords are very easily broken by those who do a Google
search and find the code and workbooks that are available.

Signature
Regards
Norman Harker MVP (Excel)
Sydney, Australia
njharker@optusnet.com.au
Excel and Word Function Lists (Classifications, Syntax and Arguments)
available free to good homes.
> I have 2 Worksheets within a excel doc,
> I have sensitive data in the 2nd worksheet,
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> Cheers
> Chris