Function module GET_GLOBALS_FROM_SLVC_FULLSCR issue

Hi experts,

I am using the below code,

CALLFUNCTION'REUSE_ALV_GRID_DISPLAY'

       EXPORTING

         i_callback_program      = sy-cprog

         i_callback_user_command = 'USER_COMMAND'    <--------------- for this

         i_callback_top_of_page  = 'TITLE'

         is_layout               = gd_layout

         it_fieldcat             = it_fieldcat

         i_save                  = 'X'

       TABLES

         t_outtab                = it_final

       EXCEPTIONS

         program_error           = 1

         OTHERS                  = 2.

     IF sy-subrc = 1.

       MESSAGE'Program Error'(004) TYPE'E'.

     ENDIF.

     REFRESH: it_fieldcat.

   ENDIF.

FORM user_command USING r_ucomm   TYPE sy-ucomm

                         sel_field TYPE slis_selfield.

   DATA: it_grid TYPEREFTO cl_gui_alv_grid,

         lv_is_valid.

   DATA: lv_flag_crt TYPE char1,

         lv_flag_chg TYPE char1.

   CALLFUNCTION'GET_GLOBALS_FROM_SLVC_FULLSCR'

     IMPORTING

       e_grid = it_grid.

   CALLMETHOD it_grid->check_changed_data

     IMPORTING

       e_valid = lv_is_valid.

if lv_is_valid is not initial and r_ucomm = '&DATA_SAVE'.

Success message .

endif.

The problem is always i am getting lv_is_valid is 'X'. whenever the it_grid get filled lv_is_valid become 'X'.

I need only when there is a change in inputfields of report output(editable columns).  Now always i am getting success message.

Please suggest me a solution.

Thanks & regards

Venkat