do I have to manually change PER to amortize a loan out 40 years?

[ldk]

I'm amortizing 40-year notes using PPMT to calculate the principal payment.
For each monthly payment I have to manually change PER in the formula to
update the schedule. Is there another way to do this? I'm using Excel 2003.

[Morrigan]

You can replace PER with ROW() if 1st payment being on row1, or ROW()-1 if payment being on row2, etc.

I'm amortizing 40-year notes using PPMT to calculate the principal payment.
For each monthly payment I have to manually change PER in the formula to
update the schedule. Is there another way to do this? I'm using Excel 2003.