Help with registerattached Dependency Property
===

I created my own DataGrid control which inherits the DataGrid. I declared a Dependency Property which I want to use at column level, so On PreviewKeyDown event, I check the value and decide if this current cell need to be handled or not.

    public class MyDataGrid : DataGrid
    {
        public static DependencyProperty HandleKeyPressEventProperty =
           DependencyProperty.RegisterAttached("HandleKeyPressEvent", typeof(bool), typeof(MyDataGrid),
                    new FrameworkPropertyMetadata(true));

        public bool HandleKeyPressEvent
        {
            get { return (bool)GetValue(HandleKeyPressEventProperty); }
            set { SetValue(HandleKeyPressEventProperty, value); }
        }

        protected override void OnPreviewKeyDown(KeyEventArgs e)
        {
            if (HandleKeyPressEvent)
            {
                HandleKeyPress(e);
            }
            else
            {
                base.OnPreviewKeyDown(e);
            }
        }
    }
    

At xaml I use it like this:

    <MyDataGrid x:Name="myDataGrid">
       <DataGridTextColumn MyDataGrid.HandleKeyPressEvent = "True" />
       <DataGridTemplateColumn MyDataGrid.HandleKeyPressEvent = "False"/>
    </MyDataGrid>

But I am having real problem to have this dependancy proporty available at column level. What I try to do is just like `Grid.Column`. Can someone help me with that? 
Thanks
Jing
