esto es lo que tienes ok .. esta bien lo unico q deberias d hacer es lo siguiente
CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
EXPORTING
IT_FIELDCAT = IT_FIELDCAT
I_CALLBACK_USER_COMMAND = 'USER_COMMAND'
IS_LAYOUT = GS_LAYOUT
TABLES
T_OUTTAB = IT_OUT
*------------------------------------------------------------------------
*---------------------------------------------------------------------*
* FORM user_command *
*---------------------------------------------------------------------*
* ........ *
*---------------------------------------------------------------------*
* --> PA_UCOMM *
* --> PA_TABLA *
*---------------------------------------------------------------------*
FORM user_command USING pa_ucomm LIKE sy-ucomm
pa_tabla TYPE slis_selfield.
WHEN '&IC1'.
CHECK NOT pa_tabla-value IS INITIAL.
READ TABLE IT_OUT INDEX pa_tabla-tabindex.
CASE pa_tabla-sel_tab_field.
WHEN 'IT_OUT-tucampo'.
SET PARAMETER ID 'BLN' FIELD pa_tabla-value.
-- tus valor o pedido de compra
CALL TRANSACTION 'tu transaccion' AND SKIP FIRST SCREEN.

ENDFORM