var currentRect = 1;

function CanvasLoaded(sender, args)
{
    var storyboard = getXamlElement("wpfeControl1", "story1");    
    storyboard.Begin();
}
function StoryboardCompleted(sender, args)
{
    if (++currentRect > 3)
    {
        currentRect = 1;
    }
    var name = "story" + currentRect;
    var storyboard = getXamlElement("wpfeControl1", name);       
    storyboard.Begin(); 
}