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 145.75th installment in their series of digital spreadsheet magic tricks, you'll learn how to use the AVERAGEIF (AVERAGE IF) function to create a formula that will calculate the average when you have more than 1 criterion.