How to move multiple border control which we are creating dynamically over a stackpanel?

Hello! Greeting to all of you!

We are trying to move multiple border control dynamically with in a stack panel. It works partially and sometime it gets stuck and mouse gets stick with the control even we release...

Here is the code we are using.. Please suggest on the resolution or give us pointer.. Any help in this regard will be much appreciated?

Point positionWithinImage;
Point StackPanelpositionWithinImage;
bool holding = false;

private void Panel_PointerPressed(object sender, PointerRoutedEventArgs e)
{
    holding = true;
    objBorder.Name = (sender as Border).Name;
    (sender as Border).PointerMoved += PanelView1_PointerMoved;
    positionWithinImage = e.GetCurrentPoint(sender as Border).Position;
    (sender as Border).PointerExited += Dashboard_PointerExited;
}

private void Dashboard_PointerExited(object sender, PointerRoutedEventArgs e)
{
    holding = false;
    (sender as Border).PointerMoved -= PanelView1_PointerMoved;
    (sender as Border).PointerExited -= Dashboard_PointerExited;
}

private void PanelView1_PointerMoved(object sender, PointerRoutedEventArgs e)
{
    if (holding)
    {
    Border b = ((sender) as Border);
    var pos = e.GetCurrentPoint(sender as Border).Position;
    b.Margin = new Thickness((sender as Border).Margin.Left + (pos.X - this.positionWithinImage.X), (sender as Border).Margin.Top + (pos.Y - this.positionWithinImage.Y), 0, 0);
    }
}