I'm looking for a Biweekly Loan Amortization Schedule that will allow me to input various additional payments depending on ability. Loan amortization schedule. 3.4, Enter values, Loan summary. A biweekly amortization schedule is a table that details your loan payments every two weeks instead of the traditional monthly payment schedule. The tutorial shows how to build an amortization schedule in Excel to detail periodic payments on an amortizing loan or mortgage.