Workbook.Password Property (Excel)
Published: July 16, 2012
Returns or sets the password that must be supplied to open the specified workbook. Read/write String.
Use strong passwords that combine uppercase and lowercase letters, numbers, and symbols. Weak passwords don't mix these elements. Strong password: Y6dh!et5. Weak password: House27. Passwords should be 8 or more characters in length. A pass phrase that uses 14 or more characters is better. For more information, see Help protect your personal information with strong passwords. It is critical that you remember your password. If you forget your password, Microsoft cannot retrieve it. Store the passwords that you write down in a secure place away from the information that they help protect.
In this example, Microsoft Excel opens a workbook named Password.xls, sets a password for it, and then closes the workbook. This example assumes a file named "Password.xls" exists on the C:\ drive.