From Free Excel Templates:
Keep out the hassles of protecting your sensible data in excel worksheets every time by entering a password. Now manage all your excel worksheet passwords with a single master password. Just install our Excel add-ins and protect your worksheets with a single click. The add-ins automatically assigns passwords (quite robust) and nobody has a chance to figure it out except you. Just enter a single master password and you can protect any number of sheets at will. You can also always protect your worksheets when you close the workbook. Protect multiple worksheets with a single click. Define the selection criterias for each worksheet.
Version 1.1.1 includes some updates such as fixing the bug for case sensitive worksheets, restricting selection of protected cells, and includes options to break password and change your master password.