adding up figures relating to a range of cells with a month in

I have one cell to put the year in, which in turn will change the column which I have dates in –starting from 01/04/2012 to 31/03/2013). Next to that will be a figure. What I am after is to add all the figures which are next to any April date (however the cells will change when there is a leap year so I can’t fix the cells and do a normal sum).

Year 2012 in A1

Date in B1 down wards.
B1 = 28/04/2012
B2 = 29/04/2012
B3 = 30/04/2012
B4 = 31/04/2012
B5 = 01/05/2012
B6 = 02/05/2012
B7 = 03/05/2012


In column c are figures
C1 = 1
C2 = 0
C3 = 2
C4 = 4
C5 = 1
C6 = 2
C7 = 1


In column e I would like all the figures for April to be totalled up. So Aprils total would be, 7 and mays would be 4.


Thanks for any help or advice.