=SUMPRODUCT(--(MOD(ROW(A1:A99),2)=1),A1:A99)

HTH
--
AP

"Aarif" a écrit dans le message de
...
Hi,

a1,a3,a5.......... =a1+a3+a5.............

can i use a formula that calculate every next row.

Thanks in advance,

Aarif