How to make Finantial functions in PL/SQL

I need to make a math function, to give the periodic payment for an annuity based on constant payments and a constant interest rate. I have a rate per period, the total number of payment periods in an annuity and the total amount that a series of future payments is worth now, like the PMT function.
Please, if anyone know how I can take this function in PL/SQL, take me an answer.
Thank you.

Angela Maria dos Santos Received on Mon Sep 08 1997 - 00:00:00 CDT