Excel Formula to calculate all costs within a particular month for a particular category

Hi Guys,

I'm hoping you can help me with the attached spreadsheet.

Excel.xlsx

I have two worksheets where I would like total invoice costs entered into the 'Input' worksheet to be displayed in the 'Summary' worksheet for the relevant category and month.

e.g. For the 'Web' category for the month of July, the summary worksheet cell B5 should display the total cost (excl. GST) of all invoices entered into the input worksheet that are for the month of July and are categorised as 'Web'.

Can someone help me to produce this formula?

Thanks!

Jami