Oz du Soleil teaches Excel workshops and consults clients who have small businesses with no IT teams or sophisticated data management systems. He's worked with data and Excel for more than 10 years, including time spent as a financial analyst, facing issues of data quality, modeling business rules in Excel formulae, and revising reports. He lives in Chicago. Bill Jelen is the host of www.MrExcel.com, a Microsoft MVP, and writes the monthly Excel column for "Strategic Finance Magazine." He is the author of 44 books about Excel. He lives in Akron, Ohio.