Share and volume change help required

[#1]

Hi I am trying to calculate the volume change and share change.

current 4 week shows the current 4 periods-1,2,3,4

change 4 weeks is the difference = current 4 weeks(1,2,3,4) - prev 4 weeks(5,6,7,8)

same for share.

I have attached the qvw file.I am not able to calculate the change and growth propely .Plz help.