addup up a dynamic range of numbers in a column

[observer]

Guys/gals I need you help again like I did a couple years ago (which
by the way was a great help / bunch of people) so here goes....

I have an amortization schedule for a loan and in it I have a couple
of cells which will specify the beginning payment and ending payment
paid in a given year. Keep in mind these beginning and ending payment
numbers will change from year to year and in theory could be say 6
payments or 15 payments (random number of payments) in a year. I need
to calculate for these payments and in between them, the summation of
their principal or interest paid which is in a column on the schedule.
One idea I had tho it may or may not be worthy was to be able to do a
Vlookup on the beginning and ending payment number (to get say the
payment's corresponding principal or interest and sum that up as well
as in between the beginning and ending payment numbers. Like I said
earlier, this approach may not be good since I don't know how many
payments I'm dealing with ... 1, 20, 30 ????

Also please no VBA solutions since I am just a beginner more or less
with excel.

Hope I was able to get my question across clearly.
Thanks in advance !!

 

[Dave Peterson]

I don't understand the details, but you could put a formula like this in B1:
=sum(a:a)
to sum all the numbers in column A.

If there are other numbers in column A that should not be included, then this
won't work.