How can I make Groups in a Metro GridView use different Layouts?

I'm writing a Windows 8 Metro app. I'm trying to draw a GridView with three Groups. I want one of those groups to layout their items differently than the others. I've used Selectors before in WPF, so I thought that'd be a good route. So I tried the GroupStyleSelector and I found this example on MSDN :

public class ListGroupStyleSelector : GroupStyleSelector
{
  protected override GroupStyle SelectGroupStyleCore(object group, uint level)
  {
    return (GroupStyle)App.Current.Resources["listViewGroupStyle"];
  }
}

So I altered/expanded on it from something that would suit me:

CS:

public class ExampleListGroupStyleSelector : GroupStyleSelector
{
  public ExampleListGroupStyleSelector ()
  {
     OneBigItemGroupStyle = null;
     NormalGroupStyle = null;
  }

  public GroupStyle OneBigItemGroupStyle { get; set; }
  public GroupStyle NormalGroupStyle { get; set; }

  protected override GroupStyle SelectGroupStyleCore( object group, uint level )
  {
     // a method that tries to grab an enum off the bound data object
     var exampleListType= GetExampleListType( group );

     if ( exampleListType== ExampleListType.A)
     {
        return OneBigItemGroupStyle;
     }
     if ( exampleListType== ExampleListType.B|| exampleListType== ExampleListType.B)
     {
        return NormalGroupStyle;
     }

     throw new ArgumentException( "Unexpected group type" );
  }
}

XAML:

<Page.Resources>
  <ExampleListGroupStyleSelector 
     x:Key="ExampleListGroupStyleSelector"
     OneBigItemGroupStyle="{StaticResource OneBigGroupStyle}"
     NormalGroupStyle="{StaticResource NormalGroupStyle}" />
</Page.Resources>
<GridView
     ItemsSource="{Binding Source={StaticResource exampleListsViewSource}}"
     GroupStyleSelector="{StaticResource ExampleListGroupStyleSelector}">
     <Gr