Looping animation

[nilbernator]

I animate a label to move up the screen using the following code:

private void Animate(object sender, EventArgs e)
        {
            Storyboard scrollTweets = new Storyboard();
            DoubleAnimation ani = new DoubleAnimation();
            ani.From = (double)label1.GetValue(Canvas.TopProperty);
            ani.To = (double)label1.GetValue(Canvas.TopProperty) - label1.ActualHeight;
            ani.Duration = new Duration(TimeSpan.FromSeconds(1));
            Storyboard.SetTarget(ani, label1);
            Storyboard.SetTargetProperty(ani, new PropertyPath(Canvas.TopProperty));
            scrollTweets.Children.Add(ani);
            scrollTweets.Completed += scroll_Completed;
            scrollTweets.Begin();
        }

In the complete event I try to change it's position like this:

private void scroll_Completed(object sender, EventArgs e)
        {
            label1.SetValue(Canvas.TopProperty, 400.00);
        }

This does not seem to do anything. However if I change the top property of the control before I animate it the control's position changes just fine. Is the animation doing something to the canvas property. How can I change the labels top property after animating it. Any help will be appreciated. Thanks.