Love Microsoft Excel? This clip contains a tip that just might induce you to. With this free video tutorial from ExcelIsFun, the 57th installment of his "YouTubers Love Excel" or YTLE series of free video MS Excel lessons, you'll learn how to avoid a #NUM! error when changing the formula input numbers for the NPER function. Learn to love digital spreadsheets more perfectly with the tricks outlined in this free Microsoft Office how-to.