Finding difference between column values in a matrix

I have a table that looks like this:

I want to create a new column that calculate the difference between revenue of:

1. current week - last week

2. current week - 2 weeks ago

3. current week - beginning of quarter

for each of the segment

I also want the formulas to work in a way where everytime there's a new week's data in the matrix, the values update themselves.

I tried creating a Pivot column for the weeks but it does not give me the correct value. 

Any suggestions on how I could accomplish this?

Thanks