Colin Banfield has worked in the telecommunications field for more than 20 years. He has used spreadsheet programs for over 18 years, including every version of Microsoft Excel. Colin's largest Excel project to date is a comprehensive tool designed for central office equipment configuration, pricing, and manufacturing, which is used by sales, engineering and manufacturing personnel. In his spare time, Colin enjoys photography, astronomy, chess and expanding his musical repertoire. John Walkenbach is the leading authority on spreadsheet software. He is the author of more than two dozen spreadsheet books and has written more than 300 articles and reviews for a variety of publications, including PC World, InfoWorld, Windows magazine, and PC/Computing. He is also the principal of JWalk and Associates Inc., a consulting firm that specializes in spreadsheet application development.