gaugedouble range binding

Hello,

i've a Problem by Setting the Range of an GaugeDouble with MVVM

Here is my Code that doesn't work. Hope anyboy can help me:

<ni:GaugeDouble  Range="{Binding GaugeRange}"  Value="{Binding Value}" Width="auto" />

and in my Viewmodel

 private Range<double> _GaugeRange;
         public Range<double> GaugeRange
         {
             get { return _GaugeRange; }
             set
             {
                 _GaugeRange = value;

                 NotifyPropertyChanged("GaugeRange");
             }
         }

 Thanks for your help