Hola por lo q entiendo es q quieres insertart tu propio boton excel y llamar a tu rutina para mostrar tu excel..
ok lo q tienes q hacer es insertar tu nuevo boton de la siguiente manera
paso1
excluir el boton excel q por defecto pone la barra del alv
DATA ls_toolbar_excluding TYPE ui_func.
ls_toolbar_excluding = '&LOCAL&CUT'.
INSERT ls_toolbar_excluding INTO TABLE lt_toolbar_excluding.

paso 2
declara tu metodo en tu clase ejemplo
class lcl_event_receiver definition.
public section.
METHODS handle_toolbar
FOR EVENT toolbar OF cl_gui_alv_grid
IMPORTING e_object e_interactive.
METHODS handle_user_command
FOR EVENT user_command OF cl_gui_alv_grid
IMPORTING e_ucomm.
endclass.

class lcl_event_receiver implementation.
*** otros metodos q debes de tener...
***
METHOD handle_toolbar.
PERFORM handle_toolbar CHANGING e_object.
ENDMETHOD. "handle_toolbar
METHOD handle_user_command.
PERFORM handle_user_command USING e_ucomm.
ENDMETHOD. "handle_user_command
endclass.

DONDE

FORM handle_toolbar CHANGING e_object
TYPE REF TO cl_alv_event_toolbar_set.
DATA ls_toolbar TYPE stb_button.
IF SY-SUBRC EQ 0.
CLEAR ls_toolbar.
ls_toolbar-butn_type = 3.
CLEAR ls_toolbar.
ls_toolbar-function = 'EXCEL'.
ls_toolbar-icon = ICON_XXXXXX.
ls_toolbar-quickinfo = text-008.
ls_toolbar-disabled = space.
APPEND ls_toolbar TO e_object->mt_toolbar.
ENDFORM

FORM handle_user_command USING e_ucomm TYPE sy-ucomm.
Wsyucomm = e_ucomm.
CASE Wsyucomm.
WHEN 'EXCEL'.
****AQUI PONES TU LOGICA
ENDCASE.
ENDFORM

Cuando estes por cargar tu alv.. acuerdate en
SET HANDLER event_receiver->handle_toolbar FOR grid1.
SET HANDLER event_receiver->handle_user_command FOR grid1.
.
.
.

CALL METHOD grid1->set_table_for_first_display
EXPORTING
i_structure_name = 'TI_ZTFIH'
is_layout = gs_layout
is_variant = gs_variant
i_save = ''
i_default = 'X'
it_toolbar_excluding = lt_toolbar_excluding ----ojo!!!
CHANGING
it_outtab = TI_ZTFIH[]
it_fieldcatalog = gt_fieldcat
IT_SORT = GT_SORT[].