<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>

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;
            }
        }