Regularly spaced intervals is easy enough to do:
Suppose your range goes through row 100
start = your starting row within the range, so say the first number you want
summed is in row 11, you would substitute 11 for the 2 appearances of start
in the formula, likewise, you would substitute for nth however many rows is
the regular interval.
=SUMPRODUCT(--(MOD(ROW(A1:A100)-start,nth)=0),--(ROW(A1:A100)=start),A1:A100)

If this doesn't seem to work for you, post back with column reference,
starting point, how many rows, etc.
--
** John C **


"Picman" wrote:

Yes they are at regularly spaced intervals.

"John C" wrote:

Are the cells at regularly spaced intervals?
If not, do the cells have some unique identifier in the same row that they
are in?

If not, remember, there are 30 arguments in each sum, you could nest your
sum statements:
=SUM(SUM(A1,B4,C5,...),SUM(J13,K27,M612))
--
** John C **
Please remember if your question is answered, to mark it answered :). It
helps everyone.


"Picman" wrote:

I have a column with hundreds of populated cells, and I would like to add up
the sum of more than 30 of these cells. The problem is that they are not
adjacent to each other and the Excel SUM function seems to limit the number
of arguments to 30. Is there a way around this?