Distinguish business rule violations
As you can see here, working with the time values complicates things a bit. This solution uses >.34 to represent time values greater than eight hours, which will work in most cases -- you can't use the value 8 or even the time value 8:00. You can also use the predefined Greater Than rule in Excel 2007 and 2010, which will automatically use the more accurate value of 0.333333….
Susan Sales Harkins is an IT consultant, specializing in desktop solutions. Previously, she was editor in chief for The Cobb Group, the world's largest publisher of technical journals.