cursor positon of table control in module pool

Hi

I am using table control inside tabstrip ie there is one screen (say 100 for tabstrip ) and one subscreen  (say 0011 for tablecontrol). And there is a display button on screen 100 for selection of row of table control.

for that I did coding on flow logic of subscreen as

PROCESS BEFORE OUTPUT.
* MODULE STATUS_0011.
   LOOP AT    GIT_ITEMS
         INTO    GWA_ITEMS
         WITH CONTROL ITEM_TABLE
         CURSOR ITEM_TABLE-CURRENT_LINE.
   ENDLOOP.


PROCESS AFTER INPUT.
   LOOP AT GIT_ITEMS .
     MODULE UPDATE_TABLE.
   ENDLOOP.

MODULE UPDATE_TABLE INPUT.
   READ TABLE GIT_ITEMS INTO GWA_ITEMS INDEX ITEM_TABLE-CURRENT_LINE.
   IF  MARK IS NOT INITIAL.
     GWA_ITEMS-SEL = 'X'.
     MODIFY GIT_ITEMS FROM GWA_ITEMS TRANSPORTING SEL WHERE SEL <> 'X'.
     CLEAR GWA_ITEMS.
   ENDIF.

and on screen

case sy-ucomm.

WHEN 'DIS'.
       LOOP AT  GIT_ITEMS INTO GWA_ITEMS WHERE SEL = 'X'  .
         SEL_MAT   = GWA_ITEMS-MATERIAL.
         SEL_PLANT = GWA_ITEMS-PLANT.
         SEL_DIS    = GWA_ITEMS-DECSRIP.
         SEL_SLOC  = GWA_ITEMS-S_LOC.
       ENDLOOP.

but after selecting a row mark is not getting filled(always initial)