Este Codigo te servirá:

AT SELECTION-SCREEN ON VALUE-REQUEST FOR p_vari.

CLEAR x_layout.
MOVE g_repid TO x_layout-report.

CALL FUNCTION 'LVC_VARIANT_F4'
EXPORTING
is_variant = x_layout
i_save = x_save
IMPORTING
e_exit = g_exit
es_variant = spec_layout
EXCEPTIONS
not_found = 1
OTHERS = 2.
IF sy-subrc NE 0.
MESSAGE ID sy-msgid TYPE sy-msgty NUMBER sy-msgno
WITH sy-msgv1 sy-msgv2 sy-msgv3 sy-msgv4.
ELSE.
IF g_exit NE 'X'.
p_vari = spec_layout-variant.
ENDIF.
ENDIF.

Saludos!