TRY.
CALL METHOD cl_salv_table=>factory
IMPORTING
r_salv_table = gr_salv_table
CHANGING
t_table = gt_itab.
CATCH cx_salv_msg .
ENDTRY.
CALL METHOD gr_salv_table->set_screen_popup
EXPORTING
start_column = 1
end_column = 100
start_line = 1
end_line = 20.
gr_salv_table->display( ).