procedure TForm1.FormCreate(Sender: TObject); 
begin 
  // Oder im Objektinspektor einstellen 
  // Or set in object inspector 
  ListBox1.Style := lbOwnerDrawFixed; 
end; 

procedure TForm1.ListBox1DrawItem(Control: TWinControl; Index: Integer; 
  Rect: TRect; State: TOwnerDrawState); 
var 
  l: Integer;  
  t: String; 
begin 
  with ListBox1 do 
  begin 
    Canvas.FillRect(Rect); 
    t := Items[Index];  
    l := Rect.Right - Canvas.TextWidth(t) - 1; 
    Canvas.TextOut(l, Rect.Top, t); 
  end; 
end; 

procedure TForm1.Button1Click(Sender: TObject); 
begin 
  ListBox1.Items.Add(Edit1.Text); 
end;