John Walkenbach, a.k.a "Mr. Spreadsheet," is a principal of J-Walk and Associates, Inc. and a Microsoft Excel MVP. He is a leading authority on spreadsheet software and creator of the award-winning Power Utility Pak. He has written more than 50 books, including Excel 2003 Formulas and Excel 2003 Power Programming with VBA, as well as articles and reviews for publications including PC World, InfoWorld, and Windows. He also maintains the popular Spreadsheet Page at www.j-walk.com/ss.