How to lock a spreadsheet in Sharepoint

[SheriW]

I need to lock a spreadsheet to be view only in Sharepoint.  There has to be an answer.  I don't want to make it by permissions or change library settings, just to lock or encrypt a spreadsheet.

Please help!

[#2]

I may be missing something but, it’s Excel, why wouldn’t you just use the Excel protection functionality that’s been there for 100 years?

[#3]

@BradD  thank you for the suggest that is 100 years old.  This is a document created in sharepoint and lives in sharepoint and it does not have all the options that a desktop Excel document has.

Do you have another suggest that maybe isn't as old as the first one?  I really am looking for a solution.

[#4]

@SheriW but regardless, again, it's still Excel.  I just tested it myself.

I created a new workbook, opened it in the desktop app, locked it (and it saved automatically) and then when I go back to the online view, it's locked and I cannot edit it.  You can't edit the protection in the online view but that doesn't stop you from opening it in the desktop app and making those changes.

If that's now what you're after then I'm clearly misunderstanding your issue.