Excel 2010 and 2007 users can password protect their worksheets using the General Options
Listed below are the steps to password protect an Excel worksheet.
Click the File menu –> Save As option and click the tools dropdown arrow available on the bottom of the Save As dialog box
Select General Options form the menu list
This would display the following General Options dialog box. Using the Password to open and Password to modify text fields you can specify the password required for opening or modifying an excel workbook.
After specifying the required passwords, click OK to confirm the changes.