Index / Match / Sum formula to show weekly figures

I hope you guys can help me again. I originally posted and got my answer a while ago : http://www.excelforum.com/excel-form...ml#post3457010

but now as a new year starts I want to extend the data, rather than have a sheet for each year. original question was :

attached is a returns sheets that a qty is logged against part number every week.
Some of the data I can use pivots on ( no problem ), but I have an issue on the returns tab where I think index/match / sum or something else will be better.
At the moment because of the layout of data I have to drag each week number into the pivot value, do a greater than zero filter then summarize as a sum (yuk) I just cant get my head around index/match /sum, but can someone help?
It would be great just to be able to enter a week number, and all the warehouse, part numbers and qty came through.
There is a short explanation on the returns tab of what im looking for. Thanks in advance.

so in essence I want week numbers across the top, but be able to enter a year on the returns tab that looks at the week number. I don't know enough about the formula to change.

Thanks