SAP dropdown list box for an ABAP report selection screen

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*: Report:  ZRESTRICT_SELOPT                                 :
*:                                                           :
*: Author:  www.SAPdev.co.uk                                 :
*:                                                           :
*: Date  :  2009                                             :
*:                                                           :
*: Description: Demonstrates how to display values as an SAP :
*:              dropdown listbox                             :
*:                                                           :
*:...........................................................:
REPORT ZLISTBOX.
types: begin of t_ekko,
  ebeln type ekko-ebeln,
  end of t_ekko.
data: it_ekko TYPE STANDARD TABLE OF t_ekko,
      wa_ekko like line of it_ekko.
TYPE-POOLS: VRM.
DATA: NAME  TYPE VRM_ID,
      LIST  TYPE VRM_VALUES,
      VALUE LIKE LINE OF LIST.
PARAMETERS: P_PARM(10) AS LISTBOX VISIBLE LENGTH 10.
*********************************************************
*AT SELECTION-SCREEN OUTPUT.
AT SELECTION-SCREEN OUTPUT.
  SELECT ebeln
   up to 10 rows
    from ekko
    into table it_ekko.
  loop at it_ekko into wa_ekko.
    VALUE-KEY =  wa_ekko-ebeln.
    VALUE-TEXT = wa_ekko-ebeln.
    APPEND VALUE TO LIST.
  endloop.
  NAME = 'P_PARM'.
  CALL FUNCTION 'VRM_SET_VALUES'
    EXPORTING
      ID     = NAME
      VALUES = LIST.
********************************************************
*START-OF-SELECTION.
START-OF-SELECTION.
  WRITE: / 'SELECTED VALUE KEY:', P_PARM.