formula needed - search ceels for month and then add corresponding cells

please help,

i want to write a formula that

1. looks in multiple cells to see if it matches a certain month. dates are displayed as dd/mm/yyyy.
2. if months match, then take the number in the cell next to it and add to any other matching cells.

1/08/2010 45 24/08/2010 35 1/09/2010 90

answer will be 80

if no months match then 0 or blank