// Global vars.
private double priceMin;
private double priceMax;
private int boundsTop;
private int boundsHeight;
 
public override void Plot(Graphics graphics, Rectangle bounds, double min, double max) 
{
    priceMin = min;
    priceMax = max;
    boundsTop = bounds.Top;
    boundsHeight = bounds.Height;
 
    base.Plot(graphics, bounds, min, max);
}
 
private void chart_MouseClick(object sender, MouseEventArgs e)
{
    Panel chartPanel = sender as Panel;
    if (chartPanel == null)
        return;
 
    if (e.Clicks == 1)
    {
        double price = priceMax - (e.Y-boundsTop)*(priceMax-priceMin)/boundsHeight;
        Print(Instrument.MasterInstrument.Round2TickSize(price));
    }
}