Wpf multibinding to markupextension

See more:

WPF

I have the following MarkupExtension:

public class ResourcesExtension : MarkupExtension
{
	private string _key;
	public ResourcesExtension(string key)
	{
		_key = key;
	}

	[ConstructorArgument("key")]
	public string Key
	{
		get { return _key; }
		set { _key = value; }
	}

	public override object ProvideValue(IServiceProvider serviceProvider)
	{
	return	Properties.Resources.ResourceManager.GetObject(_key);
	}
}

and I want to use it in the following XAML:

<ContentControl.Visibility>
	<MultiBinding Converter="{converters:IsTrueConverter}"
	              ConverterParameter="Visible:Collapsed">
		<Binding  Path="OverlaySettings.ShowCurrentDiopterSolution"/>
		<converters.ResourceExtension Key="ShowStatusFlags"/>
	</MultiBinding>
</ContentControl.Visibility>

I am having a hard time figuring out how to use a MarkupExtension in a Binding.

Thanks

What I have tried:

I have tried what you see above