Vista - How to pass object to XAML page

Hi,
I have a WindowsForm with a Frame and I load some page inside the frame.
The XAML of the main form is:
<Window x:Class="Sicop.Contabilita.WindowMain"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="abilita"
Height="600" Width="800" Initialized="Init">
<DockPanel LastChildFill="True">
<StackPanel DockPanel.Dock="Left" VerticalAlignment="Top"
Name="stackPanel1">
</StackPanel>
<Frame Content="" Name="frameWorkPage">
</Frame>
</DockPanel>
</Window>

I loade in the frame some page without problem with this command:
this.frameWorkPage.Navigate(new
System.Uri("ContiCorrenti/PageContiCorrentiMovimenti.Xaml",
UriKind.Relative));
and work fine, but how I can pass a parametrs to the loaded page?

I have tried using the page constructor:

ImpegniAccertamenti.iaPageElenco pageIA = new
Sicop.Contabilita.ImpegniAccertamenti.iaPageElenco(object param);
this.frameWorkPage.Navigate(pageIA);

but don't work.

I have tried witn the Navigation . I have added the event in lhe page
costructor
this.NavigationService.LoadCompleted += new
LoadCompletedEventHandler(NavigationService_LoadCompleted);
And I have created the method:
void NavigationService_LoadCompleted(object sender, NavigationEventArgs e)
{
this._IA = 'I';
}

But I get a null reference exception System.NullReferenceException {"Object
reference not set to an instance of an object."}


Thanks.
Lorenzo Soncini