[Display(Name = "Totale")]
public decimal TotaleCalcolato
{
            get
            {
                return Importo * Quantita;
            }
}

public class Prodotto : INotifyPropertyChanged
{
        public decimal Importo
        {
            get
            {
                return importo;
            }
            set
            {
                if (importo!= value)
                {
                    importo= value;
                    OnPropertyChanged(new PropertyChangedEventArgs("Totale"));
                }

            }
        }
  
        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(PropertyChangedEventArgs e)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, e);
        }

        ....

}