Changing Property Types in Designer

Question

Hello,

I have a property in a control that exposes an interface. IElementTemplate. What I was hoping to do was to use the designer control to override the reference to change it to a class that inherits from this interface, but this isn't working:

protected override void PreFilterProperties(System.Collections.IDictionary properties)
{
 base.PreFilterProperties(properties);

 var prop = (PropertyDescriptor)properties["TestTemplate"];
 //Change property to control template class instance

 prop = TypeDescriptor.CreateProperty(typeof(ControlElementTemplate), prop, new Attribute[] { });

 properties["TestTemplate"] = prop;
}

But this isn't working in the markup view. Is that even possible?

Thanks.