Showing BusyIndicator after clicking MenuItem option

hi, My aim is very simple. Some options in my main menu delay up to two seconds and I would like to show one BusyIndicator.

Can you give me some hint about how can I do that? I mean, I don't want to use any Backgrounworker or something like that.

xaml:

<xctk:BusyIndicator Name="espereplis" IsBusy="{Binding IsBusy}" BusyContent="Por favor espere un momento"></xctk:BusyIndicator> 

..
..
..


  <MenuItem Header="Clientes" Name="ProcesosClientes" FontFamily="Trebuchet MS"
                          FontSize="20" Foreground="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" 
                          Background="#FF99B4D1" Cursor="Hand"><MenuItem.Effect><DropShadowEffect/></MenuItem.Effect></MenuItem>

I've tried this kind of shabby code...without successfully results..

code behind:

    Private Sub ProcesosClientes_Click(sender As Object, e As RoutedEventArgs) Handles ProcesosClientes.Click

        Me.espereplis.IsBusy = True
        Thread.Sleep(1000)

        Me.Central.Visibility = Windows.Visibility.Hidden

        Me.MarcPrincipal.Visibility = Windows.Visibility.Visible
        Me.MarcPrincipal.Source = New Uri("Customers.xaml", UriKind.RelativeOrAbsolute)

Primary platform is Windows 7 Ultimate 64 bit along with VS 2012/Sql2k8 for WPF and SilverLight stuff