SAP/ABAP: Exclude buttons from selection-screen

AT SELECTION-SCREEN OUTPUT.

  DATA: it_ucomm TYPE TABLE OF sy-ucomm.

  APPEND :
    'PRIN' TO it_ucomm,  "for print
    'SPOS' TO it_ucomm,
    'ONLI' TO it_ucomm,  "for execute
    'E'    TO it_ucomm,  "for back
    'ENDE' TO it_ucomm,  "for exit
    'ECAN' TO it_ucomm.  "for cancel

  CALL FUNCTION 'RS_SET_SELSCREEN_STATUS'
    EXPORTING
      p_status  = sy-pfkey
    TABLES
      p_exclude = it_ucomm.