I'd like to place a validation error icon in the ContentPane HeaderTemplate.  I use IDataErrorInfo.Error validation, ONLY the Error() method, not the field indexer, via one or more BindingGroup.UpdateSources() calls.  I tried using ValidationAdornerSite (and SiteFor), but HeaderTemplate access is problematic as a ContentPane morphs between the Doc Host and floating, pinned, unpinned, also during which the adorner did not stay visible, so I've abandoned the adorner approach.

At this point I'm looking for creative ideas to access validation errors in the contentpane headertemplate.  I can't just bind to DataContext.Error because I only want the error icon to show after the UpdateSources calls.  Otherwise, it would show initially, which I don't want.

Any ideas welcome.  Thanks.