Take a look at Domenic's first solution. It is a generic version of
RD's. Use RD's multiplication technique and there is no need for the
double-negation. To me it seems that there's a subset of people who
design their formulas around the question "OK, how can I stick in a
double-negation in the answer?"

=SUMPRODUCT((MOD(ROW(A3:A12)-ROW(A3),8)=0)*(A3:A12))
Of course, personally, I am indifferent between the above and the array
formula
=SUM(IF(MOD(ROW(A3:A12)-ROW(A3),8)=0,A3:A12))

--
Regards,

Tushar Mehta
www.tushar-mehta.com
Excel, PowerPoint, and VBA add-ins, tutorials
Custom MS Office productivity solutions

In article , no-
says...
In news:microsoft.public.excel.worksheet.functions, "RagDyeR"
posted on Sat, 22 Jan 2005 13:21:14 -0800:

You should now be able to understand why all of the 3 formulas I entered
above will work for your situation.

Jeez. Seems like it would make more sense to have a "step" command in
Excel.

=SUM(T12:T428(STEP(8))

Or something like that. :-)

Thanks for the information. I will study it carefully.

Damaeus