How To Password Protect An Excel Workbook
You may have workbooks with sensitive information that you don't want others to see. Excel allows you to save a workbook so that a password must be used to open or modify it.
1) For Excel 2007: Click the Office Button, Save As, select the workbook type you want to save. At the bottom left-hand corner of the Save As dialog, click the Tools button.
For Excel 2000-Excel 2003: Click File, Save As. In the Save As dialog box select Tools (from the toolbar) and General Options.
2) Type a password in the 'Password to modify' box to prevent a user from making changes to the file. The user can still save the file with a different name.
3) If you select the 'Read-only recommended' option, the user will be prompted to open the file as read-only unless changes will be made. You can use this option without requiring a password.Keep in mind that this type of protection will keep most people from accessing your workbook but it is not really secure. If someone wants to access your data they can use one of the many commercial password-breaking software programs available.
Caution: If you assign password protection to a workbook and then forget the password, you cannot open the workbook, access its data through links in another workbook, remove protection from the workbook, or recover data from the workbook. Keep a list of passwords and corresponding workbooks in a safe place.