field symbol with top of page in reuse_alv_list

When using the top_of_page in REUSE_ALV_LIST_DISPLAY

I had in the old programm reference to values in the outtab for the header in the new programm I use dynamic tables and I wonder how to add those values in a header.

    CALL FUNCTION 'REUSE_ALV_LIST_DISPLAY'
         EXPORTING
              i_callback_program       = h_repid
              i_callback_pf_status_set = 'SET_PF_STATUS'
              i_callback_user_command  = 'USER_COMMAND'
*            i_structure_name         = 'ZDOORBEL_ALV'
*            IT_EVENTS                = TEVENTS
              is_layout                = slayout
              it_fieldcat              = it_fieldcat[]
              it_sort                  = tsort[]
              i_save                   = a_save
              is_variant               = variant

         TABLES
              t_outtab                 = <ta_output>
  .

in my top_of_page I try to read the current row of <ta_output> but I have no clue on how to do it. I gives the error that there is no workarea assigned to <ta_output>

anybody knows how to read the current line of <ta_output> in top_of_page ?

kind regards

arthur de smidt