WRITE STATEMENT IS GETTING EXECUTED BUT NOT GETTING DISPLAYED

HII All,

i hv created a selection screen with push button. Now when i m clicking that pushbutton, output is not getting displayed..when i debug program ,control enters in switch case and also executes write statement but write statement is not getting displayed.. below is the code ..

SELECTION-SCREEN BEGIN OF BLOCK INPUT WITH FRAME TITLE TEXT-001.

  SELECTION-SCREEN PUSHBUTTON 10(20) TEXT-002  USER-COMMAND FIR.
  SELECTION-SCREEN PUSHBUTTON 35(20) TEXT-003  USER-COMMAND SECOND.

SELECTION-SCREEN END OF BLOCK INPUT.
        
       WA-EMP_NO = 123.       
        WA-EMP_CO = 'A'.
        WA-EMP_N = 'APOORV'.
        APPEND WA TO IT_TAB.

AT SELECTION-SCREEN.

CASE SY-UCOMM.
 WHEN 'FIR'.
PERFORM SUB1.

WHEN 'SECOND'.

        APPEND LINES OF IT_TAB FROM 2 TO 3 TO IT_TAB1.
        WRITE:/ 'SECOND INTERNAL TABLE CONTENTS'.
        LOOP AT IT_TAB1 INTO WA1.
        WRITE:/15 SY-TABIX, WA1-EMP_NO NO-ZERO, WA1-EMP_CO, WA1-EMP_N.
        ENDLOOP.
ENDCASE.

FORM SUB1.
 LOOP AT IT_TAB INTO WA.
          WRITE:/ SY-TABIX, WA-EMP_NO NO-ZERO, WA-EMP_CO, WA-EMP_N.
 ENDLOOP.
ENDFORM.

Plz help me..

Edited by: Julius Bussche on Jan 29, 2009 1:40 PM

Code tags added and please dont use Caps-Lock.