Created attachment 644 [details]
Red point indicates click

Using the following code:

    Random random = new Random();
    Tower series;
    private void InitializeChart()
    {
      series = new Tower(tChart1.Chart);

      series.UseColorRange = false;
      series.UsePalette = true;

      for (int i = 0; i < 2; i++)
      {
        for (int j = 0; j < 2; j++)
        {
          series.Add(i, random.Next(100), j);
        }
      }

      tChart1.MouseClick += TChart1_MouseClick;
    }

    private void TChart1_MouseClick(object sender, MouseEventArgs e)
    {
      int index = series.Clicked(e.X, e.Y);
      if (index > -1)
        tChart1.Header.Text = "Index: " + index.ToString() + " " + "YValue: " + series.YValues[index].ToString();
    }

and clicking on the red point in the attached image returns an erroneous index number, the index number of bar behind.