Calculationg number of items sold after a specific date

Hi Guys

I am trying to calculate for each row in a spreadhseet, how many items have been sold after a specific week ending date.

I have attached an example to make it easier to understand.

Column T in the spreadsheet specifies that from which week ending date that I want to calculate how many items have been sold. I then need the value returning in the yellow cell for each of the rows.

Any help would be much appreciated.

Cheers