MVVM and keybinding

I have this form in my MVVM application.

<UserControl xmlns:behaviors="clr-namespace:....">
  ....<UserControl.InputBindings><KeyBinding Key="D1" Command="{Binding KeyCommand}" CommandParameter="{x:Static behaviors:HotKeyCommand.Random}"/></UserControl.InputBindings><Grid>
		...<TextBox Name="N1"  behaviors:TextBoxBehavior.Check="true">
		...</Grid></UserControl>

In "behaviors" setallowed keys input for TextBox:

private static void CheckPreviewKeyDown(object sender, KeyEventArgs e)
        {
            switch (e.Key)
            {
                case Key.NumPad0:
                case Key.NumPad1:
                case Key.NumPad2:
                    break;
                default:
                    e.Handled = true;
                    break;
            }
        }