If I read this right something like the following formula might work

=IF(ISBLANK(A13),"",SUM($A$10:A13)+$B$13)
if your payments start in A10 and continue down the A column and the
principla is in B13

as you copy down the formula it is anchored at A10 but the A13 will continue
to incriment down

Hope this helps

David

"phooey" wrote:

I'm doing an amortization.

I have everything working except I want to do a 'payoff' cell....

The payoff will be the sum of payments plus the principal balance.

How can I have this cell update and change as new payments are made?

IE.... if 5 pmts are made, payoff is sum of 5 payments plus the principal
balance.

If 6 pmts are made, its the sum of 6 payments plus the new principal balance.

I only want to count the principal balance if there is a corresponding
payment,
if there is not payment then payoff stops at the last payment made