add to a cell on a list based on two criteria
 

I have a list of expenses (fuel, insurances, work expenses etc. etc...) and
monthly totals to the right. I have two drop-down list for expenses one for
the month and another cell i would like to be able to input an amount and
have it added to it corresponding cell next to it's category and under the
correct month. I have tried sumif but it looks like it's not the right one