radio button on selection screen

I got 4 radio button on the selection screen and  i have to  call the transaction code or submit the report when i click on one of the radio button and press execute(f8).

my code

  IF rb4 = 'X'. " when i execute the report and click the radio button it directly call the program

   CALL TRANSACTION 'ZVAR_POS_TAX' AND SKIP FIRST SCREEN.

  ENDIF.

and my requirement to select the radio button and then execute.