MVVM Basic Binding - reflecting multiple targets

I have a ViewModel implementing INotifyPropertyChanged interface and have at least two properties Value and IsChanged. When I bind two Textboxes to the Value on source and one check box to IsChanged property of the source I noticed that user changes to Value does not reflect the other target controls!

This behavior is due to the fact that my ViewModel was not provided as a field in my container ViewModel and rather it was created when needed.

public PandViewModel PandViewModel
{
   get
   {
       return listIndex < 0
       ? null
        : new PandViewModel(panden[listIndex]);
   }
}

Moving the PandViewModel to a local field in this container class, or even putting it into an ObservableCollection will sort out the problem:

public PandViewModel PandViewModel
{
    get
    {
        return listIndex < 0
        ? null
        : pandenVM[listIndex];
    }
}

See also a nice article over Binding on MSDN.