>You could wire up the changed event in the window constructor:

    foreach (var c in DataGridItemsSourceCollection)
>      {
>        c.PropertyChanged += CollectionItemChanged;
>      }

then, with the textbox wired to 'TotalAmt:

   void CollectionItemChanged(object sender, PropertyChangedEventArgs e)
>    {
>      if (e.PropertyName == "awd_amount")
>      {
>        TotalAmt = DataGridItemsSourceCollection.Sum(x => x.awd_amount);
>        OnPropertyChanged(new PropertyChangedEventArgs("TotalAmt"));
>      }
>    }

Quick and dirty - there may be more elegant ways :-{

Thanks Viv,

I have been using a plain unbound textbox to display the total. Do I need to somehow declare TotalAmt as a property of something and bind the textbox to that? If so, should this be a property of the form? or of my Business Object (BO)?

Basically I have AirWayBill is my main BO and AirWayBillDetail is a child of BO. Do I need to create a TotalAmt property on AirWayBill in order to get this to work?