Is there a worksheet function or a custome function to calculate the interest
owing from date on a loan.

If the loan is amorized over 36 months and say the principal is $1000.00 and
the monthly payment is $250.00 (made up). But the borrower only makes
$100.00 every month (which will only cover part of the interest - nothing
will go to principal). After six months, How can I calcuate the interest
owing from date.
- we have to account for interest rate changes.
- Payments made that may have applied to principal as well
- interest only payments made with different interest rates.

If no one has the answer.. Is there a resource center (web site) I can go to
find the answeres.

Thank you