I dont know the specifics of what you'd like to offer but...You can use
simple interest (original(or current) amount *interest rate/12) for the
interest payment for the first 5 years, and the PMT formula for the payment
amounts after 5 years.

EX:

300,000 mortgage
360 months
6%

=300k*.06/12 = $1,500(initial pmt of interest only for first 60 months)
then for remaining 300 months payment amount...
=PMT(0.06/12,300,300k) = $1,932.90

this assumes total payoff in 360 months.

There is no need to use the payment formula for the first 5 years as you
only need the interest due.



hth,
Dave

"origin8r" wrote:

I have a spreadsheet that takes everyones current mortgage amounts and
calculates their new payments at my "advertised" rate. What I'd like to do
is find a formula to determine how to figure an interest only payment based
off of the standard =pmt(rate,nper,pv) formula. Assuming that the loan will
be interest only for the first 5 years of the loan.
Thanks for any advice!