Home Insert Page Layout Formulas Data Review View Help L34. 7 In cell M11, enter a formula that will calculate the total amount due after discounts have been applied. Incorporate an IFERROR function to return a blank value ("m) if formula returns an error. Format the result as Accounting and copy the formula down through M34. In Step 7, you will multiply 111 by 1 minus the sum of J11:L11 (use parenthesis). Then wrap the function in an IFERROR to return a blank..