MODULE user_command_0100 INPUT.
DATA(lv_ok) = ok_code.
CLEAR ok_code.

CASE lv_ok.
WHEN 'BACK' OR 'EXIT' OR 'CANCEL'. 
LEAVE TO SCREEN 0.
WHEN 'NEXT'. 
IF gv_idx < lines( gt_speisen ). gv_idx = gv_idx + 1. ENDIF.
WHEN 'PREV'.
IF gv_idx > 1. gv_idx = gv_idx - 1. ENDIF.
WHEN 'EDIT'.
CALL SCREEN 200 STARTING AT 10 5.
ENDCASE.
ENDMODULE.