Open the Excel file
Click File
Click Info
Click Protect Workbook
Select Mark as Final
Save the file
Open the Excel file
Click File
Click Save As
Click Tools
Click General Options
Check Read-only recommended
Click OK
Save the file
Open the Excel file
Click File
Click Save As
Click Tools
Click General Options
Set a password to modify
Click OK
Save the file
Right-click the Excel file
Click Properties
Check Read-only
Click Apply
Click OK