I need to know how much cell B is in total for the month januar, feb etc indivudual

example
A B
01-01-06 10
05-01-06 20
25-01-06 10
02-02-06 15
15-02-06 20
28-02-06 20

Answer for Janu must be 40 en Feb 55

Does someone know a formule for this?