Calculating WoW% in SSRS

Hi - I have below data in my table.

Year     Quarter    Week   Revenue
=====================
2012   Q4            40        $40
2012   Q4            40        $45
2012   Q4            41        $50
2012   Q4            41        $90
2013   Q4            40        $40
2013   Q4            40        $40
2013   Q4            40        $40
2013   Q4            41        $40
2013   Q4            41        $40
2013   Q4            41        $40

Now, I need to generate the SSRS report with the below format:

Week                 2012         2013      WoW%
===========================
40                      $95           $120     ($120-$95)/$95

41                      $140          $120    ($120-$140)/$140

I have created the row group on Week and Column group on Year&Quarter and its displaying the data correctly.  However, I am stuck at calculating the WoW% above.  It need to be calculated based on below forumula:

(Current/ Latest years week revenue - Previous years week revenue)/(Previous years week revenue)

Could you help me in caluclating this at SSRS level.  Or Do I need to do it at SQL query level.

Thanks