New Post: Access the ViewModel of a property

Hi,
I'm not sure exactly what you are trying to do.
Does the sample "Data/PropertyGrid/UsingSelectedObjects/UsingAttributes" from the "LiveExplorer App", available here: https://wpftoolkit.codeplex.com/ helps ?
It contains an Editor Attribute : "FirstNameEditor" which is called to set an editor for a specific property. In it, the "ResolveEditor" method uses the "propertyItem.Instance" to have access to the user object (and all its properties).

You could always post some code to help.