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 497th installment in their series of digital spreadsheet magic tricks, you'll see a formula that uses SUMIFS or SUMPRODUCT functions that will take invoice information for inventory quantity sold and update inventory records to show correct amount on hand (in stock) for each store or branch of the company.