Not Sure what formula will complete the task?? Combination of formulas??

Hi there,

I am currently trying to set up a cash flow sheet fro some house construction costs.
I have attached a copy of part of the sheet I need help with.

Basically I have listed the items of work, and am puttign a number beside each (when the item will be paid for, ie week 1, week 2 etc.
The actual amount is the in another column within each row.

Therefore at the bottom I want to know the total amount to be paid in week 1, week 2 etc.

Im guessign this is a mixture of formulas??
Any help would be appreciated.
Excel Help.xlsxExcel Help.xlsx
Thanks
Adrian