Why are not pop up message window when message type I and W

Question

Hi All,
I am working in BADI ( me_purchdoc_posted~posted) for t-code ME21N. Actually i want show material number, material description  and ABC indicator of material at saving point of PO if material is significant.
code is properly working  but does not showing  error message window when I am using message type I  (information) or W (worming message) .
if i am using message type E ( error message )then showing message window just link  Information message.
So i can no understand why are not message window pop up  when i take message type I and W.
my code is that
method IF_EX_ME_PURCHDOC_POSTED~POSTED
IF SY-TCODE EQ 'ME21N' OR SY-TCODE EQ'ME21'.
  DATA : wa LIKE LINE OF IM_EKPO.
  DATA : VAR_MAKTX TYPE MAKT-MAKTX.
  DATA : VAR_MAABC TYPE MARC-MAABC.
  DATA : P TYPE STRING.
  DATA : P1 TYPE STRING.
  LOOP AT IM_EKPO INTO wa.
    SELECT SINGLE MAABC FROM MARC INTO VAR_MAABC WHERE matnr EQ wa-matnr AND werks EQ wa-werks.
    SELECT SINGLE MAKTX FROM MAKT INTO VAR_MAKTX WHERE matnr EQ wa-matnr. " AND werks EQ wa-werks.
      IF VAR_MAABC EQ 'A'.
        P = 'is significant material'.
        CONCATENATE  WA-MATNR '(' VAR_MAKTX ')'  P INTO P1.
        MESSAGE P1 TYPE 'E'.
        EXIT.
        ENDIF.
  ENDLOOP.
ENDIF.
endmethod.
guide me...............

Answer 1

Hi vinod,
thanks for reply......
yes,  my  requirement is to show the popup window with  material number, material description and ABC indicator of material at saving point of PO if material is significant.
I find Badi to transaction me21n at saving PO.  Badi ME_PROCESS_PO_CUST does not exist.
so i am using Badi me_purchdoc_posted~posted.
This Badi  ( me_purchdoc_posted~posted ) is properly working But showing message  "system error ( error in method po_post ) "
when I am click on OK then automatic leave from transaction.
guide me..........