Create 'readonly' Excel file
Create or open your Excel document
Go to File в†’ Save As and select the destination folder
Click theВ Tools button in theВ SaveВ As dialog box and then choose General Options...
In the Password to modify box, enter a password, check Read-only recommended and click OK
Reenter the password and click on OK
Enter a file name and click Save
Your Microsoft Excel document is now saved in the unencrypted form. Your file is read-only now.
Read this note on how
to unprotect Excel files.