New to Microsoft Excel? Looking for a tip? How about a tip so mind-blowingly useful as to qualify as a magic trick? You're in luck. In this MS Excel tutorial from ExcelIsFun, the 298th installment in their series of digital spreadsheet magic tricks, you'll learn how to use the SUMPRODUCT and MOD function to add up all hours in one cell worked by employees when time in and time out data are entered as time values.