How do I set up my amortization based on date paid?

From: teripatterson (teripatterson_at_discussions.microsoft.com)
Date: 10/10/04 

Date: Sun, 10 Oct 2004 16:37:01 -0700

I use the Excel Loan Calculator with Extra Payment template often. It shows
the actual principal and interest per payment. How do I formulate the
principal and interest based on the date the payment was made?