=SUMPRODUCT(--(MONTH($E$11:$E$21)="1"*(F11:F21)))


"1" = January, adjust your range as need

hth
--
regards from Brazil
Thanks in advance for your feedback.
Marcelo



"jengy1" escreveu:

i am trying to calulate the total intake for each month
ie january = 10
february = 6
march = 10

column a column b
date intake
01/01/09 10
01/03/09 2
11/02/09 6
12/03/09 7
12/03/09 1

please help