REPORT TEST.
DATA: FName LIKE tabfield-lfieldname.
PARAMETERS: p1 LIKE t000-cccopylock AS LISTBOX VISIBLE LENGTH 36,
            p2 LIKE (FName)         AS LISTBOX VISIBLE LENGTH 36,
            p3 LIKE (FName).
INITIALIZATION.
  FName = 'T000-CCCOPYLOCK'.
AT SELECTION-SCREEN OUTPUT.
  LOOP AT Screen.
    IF Screen-Name = 'P3'.
      " Подгоняем поля, чтоб были такие же как и у p1
      Screen-Value_Help      = '1'.
      Screen-Length          = '01'.
      Screen-Values_in_combo = '1'.
      MODIFY Screen.
    ENDIF.
  ENDLOOP.

Dropdown box with a value list from input help (recommended)

*&---------------------------------------------------------------*
*& Report DEMO_DROPDOWN_LIST_BOX                                 *
*&---------------------------------------------------------------*

REPORT demo_dropdown_list_box.

*&---------------------------------------------------------------*
*& Global Declarations                                           *
*&---------------------------------------------------------------*

* Screen Interfaces

TABLES sdyn_conn.
DATA   ok_code TYPE sy-ucomm.

* Global data

TYPES: BEGIN OF type_carrid,
         carrid type spfli-carrid,
         carrname type scarr-carrname,
       END OF type_carrid.

DATA itab_carrid TYPE STANDARD TABLE
     OF type_carrid WITH HEADER LINE.

*&---------------------------------------------------------------*
*& Processing Blocks called by the Runtime Environment           *
*&---------------------------------------------------------------*

* Event Block START-OF-SELECTION

START-OF-SELECTION.
CALL SCREEN 100.

* Dialog Module PBO

MODULE status_0100 OUTPUT.
  SET PF-STATUS 'SCREEN_100'.
ENDMODULE.

* Dialog Modules PAI

MODULE cancel INPUT.
  LEAVE PROGRAM.
ENDMODULE.

*

MODULE user_command_0100 INPUT.
  CASE ok_code.
    WHEN 'SELECTED'.
      MESSAGE i888(sabapdocu) WITH sdyn_conn-carrid.
ENDCASE.
ENDMODULE.

* Dialog Module POV

MODULE create_dropdown_box INPUT.
  SELECT carrid carrname
                FROM scarr
                INTO CORRESPONDING FIELDS OF TABLE itab_carrid.
  CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'
       EXPORTING
            retfield        = 'CARRID'
            value_org       = 'S'
       TABLES
            value_tab       = itab_carrid
       EXCEPTIONS
            parameter_error = 1
            no_values_found = 2
            OTHERS          = 3.
  IF sy-subrc <> 0.
    ...
ENDIF.
ENDMODULE.

The screen flow logic is as follows:

PROCESS BEFORE OUTPUT.

  MODULE status_0100.

PROCESS AFTER INPUT.

  MODULE cancel AT EXIT-COMMAND.
  MODULE user_command_0100.

PROCESS ON VALUE-REQUEST.

  FIELD sdyn_conn-carrid MODULE create_dropdown_box.