Use the following formulas to show the total payment, interest portion of the payment, and principal portion of the payment. Calculate a scheduled payment.Set up the amortization table. The indepth Watch Me Build is a 25 minute behemoth, showing you how to build a more complex, dynamic amortization table in Excel. Almost any data field on this form may be calculated. Often overlooked is the amortization schedule when calculating payments. Create a flexible amortization schedule which allows for "extra payments" and looks professional. View Amortization Table. Related.