=SUMPRODUCT(--(MOD(ROW(A1:A1000),3)=1),A1:A1000)

"ezil" wrote:

The formula "=countif(a1:a1000,"A??")" is working, but i have to count every
3rd row from a1 to a1000 like a1,a4,a7 etc., How to write formula to do this
task.
Thanks for reply