Render a custom attached property value - wpf

Question

I need to do this in XAML :
<Grid x:Name="layoutRoot">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<SomeUserControl Grid.Row="0" />
<ui:AdditionalView.UseCase1>
<ContentControl>
<TextBlock>aaa</TextBlock>
</ContentControl>
</ui:AdditionalView.UseCase1>
</Grid>
First, and most important, I need to have the block in the Something.UseCase1 form. That is how I ended up using attached properties. I defined the AdditionalView class and defined an attached property called UseCase1 on it.
However this does not render the
<TextBlock>aaa</TextBlock>
at runtime.
How can I achieve this?
Later Edit (1) - I managed to get something to work like so :
<ContentControl Grid.Row="1" Content="{Binding ElementName=layoutRoot, Path=(ui:AdditionalView.UseCase1)}" />
.. but it seems nasty. Any decent way to get this to work?
The AdditionalView class :
public class AdditionalView
{
public static readonly DependencyProperty UseCase1Property = DependencyProperty.RegisterAttached(
"UseCase1",
typeof(object),
typeof(AdditionalView),
new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender)
);
public static void SetUseCase1(UIElement element, Boolean value)
{
element.SetValue(UseCase1Property, value);
}
public static object GetUseCase1(UIElement element)
{
return element.GetValue(UseCase1Property);
}
}