forgotton password for excel file

There is a way to view it in a new spreadsheet (SS), so knowing the password is not a factor. What is a factor is knowing the content structure of the locked password, for example the sheet names.

Open a new SS and save it in the same folder as the locked on. Then in cell A1 type =[lockedss.xls]Sheet1!$A$1. It must start with the equal sign and the filename is incloded in braces; if the worksheets use custom names you have to know them.

This by far a long shot, all you need to do is either be smart and/or open your wallet.

There are many programs that can do a brute-force attack on your file to test all the combinations that your password could be, however some may require costs to retrieve the full file. You may need to leave these programs running for days.

eg
http://dmoz.org/Computers/Security/Products_and_Tools/Password_Recovery/
http://www.freedownloadscenter.com/Utilities/Misc__Utilities/Excel_Password.html