I'm looking for a Biweekly Loan Amortization Schedule that will allow me to input various additional payments depending on ability. Fill in the "Period" column.Fill in the column titled "Period" with your payment dates. This spreadsheet creates an amortization schedule for a fixed-rate loan, with optional extra payments. The tutorial shows how to build an amortization schedule in Excel to detail periodic payments on an amortizing loan or mortgage. A biweekly amortization schedule is a table that details your loan payments every two weeks instead of the traditional monthly payment schedule.