How to code for select all& deselect all?using menu buttons

Question

hai,
i have generated a report with a single field from a database table and
i have a checkbox for each record/item in the report.
i need help in the following ..
now that i have menu buttons say "select all" and "deselect all"..
if select all is clicked then all checkboxes should be selected.
if deselect all is clicked, then all checkboxes should be deselected
i know that we have to use functional code and use case sy-ucomm etc.
when "selectall"  etc..
can someone help me how to code for this to work exactly?

Answer 1

it did not work for the code u had suggested...
plz check it out and send me the exact working code..
REPORT  ZINTRACTIVE_PROJ                        .
TABLES : SFLIGHT.
DATA : BEGIN OF IT OCCURS 0,
       CARRID LIKE SFLIGHT-CARRID, FLDATE LIKE SFLIGHT-FLDATE,
       END OF IT.
DATA : BOX TYPE C,
       LINE TYPE I.
SELECT CARRID FLDATE FROM SFLIGHT INTO TABLE IT.
LOOP AT IT.
WRITE : / BOX AS CHECKBOX, IT-CARRID.
ENDLOOP.
LINE = SY-LINNO .
SET PF-STATUS 'SELECT'.
AT USER-COMMAND.
CASE SY-UCOMM.
  WHEN 'SELECT'.
      DO LINE TIMES.
        READ LINE SY-INDEX FIELD VALUE BOX.
        IF BOX = 'X'.
           NEW-PAGE.
           WRITE : / IT-FLDATE.
        ENDIF.
      ENDDO.
  <b>WHEN 'SELECTALL'.
      LOOP AT IT.
        IT-CARRID = 'X'.
        MODIFY IT TRANSPORTING CARRID WHERE CARRID = IT-CARRID.
        EXIT.
      ENDLOOP.
  WHEN 'DESELECTALL'.
      LOOP AT IT.
        IT-CARRID = ''.
        MODIFY IT TRANSPORTING CARRID WHERE CARRID = 'X'.
        EXIT.
      ENDLOOP.</b>ENDCASE.