How to call a Editor in oracle form

Declare
    v_reson varchar2(200);
    vResult boolean;
Begin
    v_reson := :outwdclr.REJECT_RESON;--assign item
    Show_Editor( 'ED_REASON', v_reson, 450, 150, v_reson, vResult); --editor name assign variable width hight
   
    If vResult then
       
        iF v_reson IS NULL THEN
            MSGBOX('Reject Reason Can Not Blank.');
             raise form_trigger_failure;
      else
        :outwdclr.REJECT_RESON := v_reson;
      End If; 
    Else
        raise form_trigger_failure;
    End If;

End;