Silverlight Get REAL Visible Items in a Container (WrapPanel)

In my case I have to change the state of just a few elements that are visible or partially visible of a big list in a wrappanel and I cannot force to animate 100 items instead of 12. So here is a way to make this:

<ScrollViewer x:Name="ScrollContainer"  >
     <toolkit:WrapPanel x:Name="WrappedButtons"/>
</ScrollViewer>

and the c#

UIElement MyUIE = ScrollContainer;
GeneralTransform gt = MyUIE.TransformToVisual(Application.Current.RootVisual as UIElement);
Rect rect = new Rect(gt.Transform(new Point(0, 0)), MyUIE.RenderSize);
var foundElements = VisualTreeHelper.FindElementsInHostCoordinates(rect, MyUIE);

Type MyType = typeof(Button);
if (foundElements != null)
      {
        var listBoxItem = foundElements.Where(w => w.GetType().Equals(MyType)).ToList();
         TBResult.Text = listBoxItem != null ? listBoxItem.Count.ToString() : String.Empty;
      }

And that's all try it, It successfully works.
(Of course as many tips is a mix and changes of stuffs from the internet)