Error in ALV Total

Hi Experts,

                 Am trying to add total for alv webdynpro column (WEIGHTAGE_RATING) but am not able to display total in my screen.

DATA: lo_cmp_usage TYPE REF TO if_wd_component_usage.
   DATA: lr_salv_wd_table  TYPE  REF  TO  iwci_salv_wd_table.
   DATA: lr_column_settings  TYPE  REF  TO  if_salv_wd_column_settings,
         lr_column  TYPE  REF  TO  cl_salv_wd_column,
         lt_column  TYPE  salv_wd_t_column_ref,
         ls_column  TYPE  salv_wd_s_column_ref.
   DATA: lr_function_settings  TYPE  REF  TO  cl_salv_wd_config_table.
   DATA: lr_field_settings  TYPE  REF  TO  if_salv_wd_field_settings,
         lr_field_amnt  TYPE  REF  TO  cl_salv_wd_field.
   DATA: lv_aggr_rule  TYPE  REF  TO  cl_salv_wd_aggr_rule.
   DATA: lr_sort_rule  TYPE  REF  TO  cl_salv_wd_sort_rule.

   lo_cmp_usage =   wd_this->wd_cpuse_alv_table( ).
   IF lo_cmp_usage->has_active_component( ) IS INITIAL.
     lo_cmp_usage->create_component( ).
   ENDIF.


   lr_salv_wd_table = wd_this->wd_cpifc_alv_table( ).
   lr_function_settings = lr_salv_wd_table->get_model( ).
* get reference to column settings
   lr_column_settings ?= lr_function_settings.
* get all columns
   lt_column = lr_column_settings->get_columns( ).

   lr_field_settings ?= wd_this->r_table.

   LOOP AT lt_column INTO ls_column.
     CASE ls_column-id.
       WHEN 'WEIGHTAGE_RATING'.
         CALL METHOD lr_function_settings->if_salv_wd_field_settings~get_field
           EXPORTING
             fieldname = 'WEIGHTAGE_RATING'
           RECEIVING
             value     = lr_field_amnt.

         CALL METHOD lr_field_amnt->if_salv_wd_aggr~create_aggr_rule
           EXPORTING
             aggregation_type = if_salv_wd_c_aggregation=>aggrtype_total
           RECEIVING
             value            = lv_aggr_rule.
     ENDCASE.
   ENDLOOP.