Hi,
Create one custom structure in se11 with your fields.
and provide the custom structure name in I_structure_name in reuse_alv_fieldcatalog_merge
call function 'reuse_alv_fieldcatalog_merge'
exporting
i_program_name = sy-repid
I_internal_tabname = 'int_output'
I_structure_name = 'ZSTRUCTRE'
I_client_never_display = 'X'
I_inclname = sy-repid
I_bypassing_buffer = 'X'
changing
ct_fieldcat = int_fieldcat
exceptions
inconsistent_interface = 1
program_error = 2
others = 3.