Summing two Block values in WEBI report

Hi Gurus

       We have a report requirement where in , We need to Sum the key figures from two different Tables in Webi , which have two different Fiscal Year / Period ( One based on Date A and other based on Date B) .I have tried somethng like this in Block 1 :

      =[Sum of overdue Critical Cases Closed]  Where ( BlockName() ="Block 2" )

  But am not getting any output for the above condition .

  We are on SAP BusinessObjects BI Platform 4.1 Support Pack 2 Patch 6 and I am aware that we can do Merge Variables in SP 3 and above , which is not in going to happen any sooner for us , thus need a workaround .

  Your help is much appreciated on this issue

Best Regards '

Vinay