 <p>You might be able to use <a href="http://msdn.microsoft.com/en-us/library/ms749011.aspx" rel="nofollow noreferrer">Attached Dependency Properties</a> of type AugmentedThickness and then, when they change, update the underlying properties they are intended to update. This requires all access to be performed using your Attached Properties, as simply setting the Thickness property will not use your AugmentedThickness. If necessary, you could also (though it might be a bit evil) listen for explicit changes to Thickness properties (that you didn't initiate) and force it back to the value specified by your AugmentedThickness.</p>