diff -r 84b3bf5ee3d2 -r 8b513df1b446 src/FingersDance.Control.Player/UserControlPlayer.xaml.cs
--- a/src/FingersDance.Control.Player/UserControlPlayer.xaml.cs	Wed Oct 07 17:16:46 2009 +0200
+++ b/src/FingersDance.Control.Player/UserControlPlayer.xaml.cs	Fri Oct 09 11:33:35 2009 +0200
@@ -16,6 +16,7 @@
 using Microsoft.Surface.Presentation.Controls;
 using FingersDance.ActionFactory;
 using FingersDance.Actions;
+using FingersDance.Control.TimeLine;
 using FingersDance.Views;
 using FingersDance.ViewModels;
 
@@ -183,7 +184,28 @@
         private void Play_Pause_area_DragEnter(object sender, SurfaceDragDropEventArgs e)
         {
             //Console.WriteLine("Enter");
-            Play_Pause_area.Opacity = 0.5;
+
+            // If the TimelineAnnotationView comes from a user control different from the current one, 
+            // it means that we want to add the annotation to the current list.
+            // So we check if the dragged annotation can be dragged or if it will recover any existant annotation (in this case it will not be accepted)
+            // e.Cursor.DragSource is the SurfaceListBox where the drag started from
+            SurfaceListBox slb = (SurfaceListBox)e.Cursor.DragSource;
+            // We get the instance of the UserControlSyncSource
+            UserControl syncSrc = (UserControl)((Grid)((Grid)this.Parent).Parent).Parent;
+            // and its UserControlTimeline
+            UserControlTimeLine tl = (UserControlTimeLine)((Grid)((Grid)syncSrc.Content).Children[0]).Children[0];
+            if (((Grid)((UserControl)((Grid)slb.Parent).Parent).Parent).Parent != tl)
+            {
+                // e.Cursor.Visual is the ContentControl, so its Content is the dragged TimelineAnnotationView
+                AnnotationViewModel annotationDataVM = (AnnotationViewModel)((TimelineAnnotationView)((ContentControl)e.Cursor.Visual).Content).DataContext;
+                Play_Pause_area.Background = tl.isAnnotationAccepted(annotationDataVM) ? new SolidColorBrush(Colors.Green) : new SolidColorBrush(Colors.Red);
+            }
+            else
+            {
+                Play_Pause_area.Background = new SolidColorBrush(Colors.White);
+            }
+            Play_Pause_area.Opacity = 0.3;
+
         }
 
         private void Play_Pause_area_DragLeave(object sender, SurfaceDragDropEventArgs e)