How can I implement Delay property from .Net 4.5 (described [here](http://msdn.microsoft.com/en-us/library/system.windows.data.bindingbase.delay%28v=vs.110%29.aspx)) on binding in .Net 4.0?

I know I cannot inherit from BindingBase as ProvideValue is sealed. 

I could implement MarkupExtension but it means I now have to rewrite all properties from BindingExtension is there any other way?