How to protect MS Excel file using password?

In Microsoft Excel, you can protect a single cell, group of cells on a worksheet or an entire workbook by applying password so that unauthorized person can not display as well as modify your document. You can apply two types of password.

Password to open the document:

If it is applied then you have to give the correct password to open the workbook. Otherwise you cannot open the workbook.

Password to modify the document:

If it is applied then you have to give the correct password to modify the workbook. Otherwise your workbook is opened but you cannot modify the workbook. It means that your workbook becomes read-only.

To apply a password to MS Excel document, follow the given steps:

First click on "Tools" menu and select the "Option" from drop down menu.

A windows dialog box will appear, here select the "Security" tab.

Enter first password in "Password to open" text box under "File encryption settings for this workbook" section and second password in "Password to modify" text box (if required) under" File sharing settings for the workbook" section then click "Ok" button of dialog box.

Microsoft Excel will open "Confirm Password" dialog box for the confirmation of passwords. The maximum length of password is 15 characters.

Re-enter the password to open and password to modify and click "Ok" button of Confirm Password dialog boxes one by one.

Now close the file and then reopen to test the password.

Source: http://www.computerfreetips.com/office_xp_tips/excel_document_password.html