Display list box for ALV report in ABAP

*&---------------------------------------------------------------------*
*& Report  ZA01JKGFT15
*&
*&---------------------------------------------------------------------*
*&
*&
*&---------------------------------------------------------------------*
REPORT za01jkgft15.
*Declare as LISTBOX and set visible length
PARAMETERS: p_lb1 AS LISTBOX VISIBLE LENGTH 40.

DATA: gv_name  TYPE vrm_id, "ID variable to store parameter Var name
      gt_list TYPE vrm_values,"Table to store key and value
      gv_value LIKE LINE OF gt_list.

AT SELECTION-SCREEN OUTPUT.
*Assign parameter variable name
  gv_name = 'P_LB1'.
*Set unquie key value and text
  gv_value-key = 1.
  gv_value-text = 'Listbox1'.
  APPEND gv_value TO gt_list.
  gv_value-key = 2.
  gv_value-text = 'Listbox2'.
  APPEND gv_value TO gt_list.
*Call function with below parameter
  CALL FUNCTION 'VRM_SET_VALUES'
    EXPORTING
      id     = gv_name
      values = gt_list.
  START-OF-SELECTION.

output: