private void RightToLeftMarquee(TextBlock tb)
    {
        doubleAnimation = new DoubleAnimation();
        doubleAnimation.From = -tb.Width;
        doubleAnimation.To = TickerCanvas.Width;
        doubleAnimation.RepeatBehavior = RepeatBehavior.Forever;
        doubleAnimation.Duration = new Duration(TimeSpan.FromSeconds(100));
        Storyboard.SetTargetProperty(doubleAnimation, new PropertyPath("(Canvas.Right)"));
        sb.Children.Add(doubleAnimation);
        sb.Begin(tb,true);
    }