Invoice Log - Formaula Help

Hi all

I need some help with adding/creating a formula to my invoice log and any help would be hugely appreciated.

From A6 to A17 I have the months of the year in order of our financial year (March - February).

From A23 down, I will be inserting invoice data. Each row will contain a Date (e.g. 15/03/2017) and a Price amongst other things and I need to aggregate the price values for all rows and show that aggregated price value next to the months (B6-B17) so we can see easily how much income we are expecting to invoice for each month.

I have attached the screenshot of that area of the invoice log.



Any offers of help would be hugely appreciated.

Thanks
Kris