delphi listbox控件的一个简单问题？

onchange时间，当点击某一记录时调用不同的程序。

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Label1: TLabel;
ListBox1: TListBox;
procedure ListBox1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.ListBox1Click(Sender: TObject);
begin
Label1.Caption:=ListBox1.Items[ListBox1.ItemIndex];
end;

end.