How to use CommandTarget with a custom RoutedCommand

Hi everybody,

I'm encountering problems with a RoutedCommand.
I have a RoutedCommand that looks like the following one (stored in a static class namedCommands) :

public static RoutedCommand MyRoutedCommand = new RoutedCommand();

public static void SaveFile(object sender, ExecutedRoutedEventArgs e)
{
            var dgSave = new Microsoft.Win32.SaveFileDialog();
            dgSave.Filter = "Google Maps Files (*.kml)|*.kml|All files (*.*)|*.*";
            dgSave.ShowDialog();
            // ??? What do I have to write here ?
}

In my XAML file, I have a Button beside a TextBox :

<TextBox x:Name="tboxFullPathFile" Width="300"/><Button x:Name="btBrowse" Content="Browse ..." Margin="5,0"
                        Command="{x:Static Member=m:Commands.MyRoutedCommand}" CommandTarget="{Binding ElementName=tboxFullPathFile, Path=Text}"/>

In my XAML .cs file, I added the following line :

CommandBindings.Add(new CommandBinding(Commands.MyRoutedCommand, Commands.SaveFile));

I would like the tboxFullPathFile to be filled with the path selected in the functionSave. But I don't know how I have to do and I can't use CommandParamter (I planned to use it to do other things).

Do you have an idea ?

Thanks in advance for your help.