Problem in displaying and calculating the sub totals in a classical report

Hi,

I am working on classical report in which i have to display the sub totals of purticular range present in IF condition.

I am using AT END OF statment and sum and .storing the value in two variables. I am displaying the these variables in other conndition so that it can be displayed . Here's the code:-

     ELSEIF ( PSCH EQ 'N' OR PSCH EQ 'O' OR PSCH EQ 'P' ).

       AT END OF SG.
         SUM.
          TBL2  = SBL1.
          PTBL2 = PSBL1.
       ENDAT.

Is there any way the values which are coming from SBL1,PSBL1 can be summed and stored in the TBL2 and PTBL2?