Modify screen based on check box

There are two buttons on screen
Rad1
Rad2


Both buttons are in same block and same group.

PARAMETERS      p_opt1   RADIOBUTTON GROUP gr1 DEFAULT 'X' USER-COMMAND a.
PARAMETERS :    p_opt2 RADIOBUTTON GROUP gr1.


This code will populate the variant field based on radio button selected.
 LOOP AT SCREEN.
    IF p_opt2 = gc_x.
      CLEAR p_var.
      p_var = '/EXCEL'(025).
      IF screen-name = 'P_MATNR'.       " Input parameter
        CLEAR p_matnr.
        screen-input = '0'.
        MODIFY SCREEN.
      ENDIF.
    ELSEIF p_opt1 = gc_x.
      CLEAR p_file.
      p_var = '/DEFAULT'(026).
    ENDIF.