How to Require a Password to Open an Excel Document
Microsoft Excel 2010 comes with a number of security options under the "Review" tab, but all of those merely prevent users from making changes to the data or layout of the sheet. To prevent a user from being able to open an Excel worksheet without a password, you'll need to access the "Permissions" area of the program. The permission options are available, in the same general location, for all Office 2010 programs.
Open the Excel file that you want to protect.
Click on "File" at the top of the Excel window. Select "Info" on the left side of the screen, and click on "Protect Workbook" under the "Permissions" section of the screen This will open a drop-down menu.
Select "Encrypt with Password" from the drop-down menu. Type in your password into the text field in the small "Encrypt Document" window that opened up. Click "OK."
Enter the exact same password again and click "OK." The Excel document is now password-protected.
Tips & Warnings
- If you ever need to remove the password, you will have to select the same "Encrypt with Password" option as you did to set the password. Then erase the password from the text box and click "OK."
- There is no built-in way to get a password once it has been set, so be sure to choose a password that you will remember.