SALV with Drill Down to open an Invoice

To achieve this we need to handle the event double click so check first the post: SALV Handle double click

After doing that in the implementation part we only need to call the function RV_CALL_DISPLAY_TRANSACTION passing the vbeln that must be at the table mapped to the ALV:

CLASS lcl_handler IMPLEMENTATION.
METHOD on_double_click.
READ TABLE SALVTable INTO WA_SALVTable INDEX row.
IF sy-subrc = 0.
CALL FUNCTION 'RV_CALL_DISPLAY_TRANSACTION'
EXPORTING
vbeln = WA_SALVTable-vbeln.
ENDIF.
ENDMETHOD.
ENDCLASS.