Try something like this:

For a list of numbers in Col_A

B1: =SUMPRODUCT((MOD(ROW(A1:A1000),10)=1)*A1:A1000)

Adjust range references to suit your situation.

Does that help?

***********
Regards,
Ron

XL2002, WinXP-Pro


"mcutlac" wrote:

i have to add cells evenly spaced, eg a1 + a11+a21+...+a991
how can I avoid writting all references?