using YEAR and MONTH together

Hi,

i'm trying to update a spreadsheet i created at the beginning of this year. the sheet summarises another workbook that records all of the jobs carried out by my company (we repair cranes and excavators).

currently the summary sheet is set up to only treat the workbook as containing data from a single year, but as we creep up to the new year, i need to find a way of getting the summary to pick out data relevant to a specific year.

if you take a look at the example workbook that i have included you'll see that the first sheet summarises data from the second sheet in a few ways. specifically, row 5 contains formulas for calculating the value of jobs closed in certain months. however, the forumla currently adds together all values from all years as long as they are within the particular month. how can i rewrite this formula so that it only adds together the values from a certain month in a certain year?