This is what I found online and the instructions in Sesame.  See if that makes sense.                                                              If you want to do the monthly mortgage payment calculation by hand, you'll need the monthly interest rate — just divide the annual interest rate by 12 (the number of months in a year). For example, if the annual interest rate is 4%, the monthly interest rate would be 0.33% (0.04/12 = 0.0033).


@PMT(Principal, Interest, Life)
Type: Financial
Parameters: Principal as double, Interest as double, Life as double
Returns: double
Calculates the payments due on a loan to give the loan amount (present value), the
interest rate per period and the number of payments. An interest rate of 2%, for
example, would be expressed as .02. The number of payments cannot be 0 (zero).
PaymentsDue = @PMT(PresentValue, InterestRate, NumberOfPayments)
PaymentsDue is assigned 1200.17 if PresentValue is 100,000, InterestRate is .01 and
NumberOfPayments is 180.
See Also: @IR

I am not sure if this would work.

You would have adjust the payments to twice a year to match the interest.

Then divide the payments by 6 for monthly payments.