>>>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?
>
>Don't know how you are setting up the DataContext.
>But you could put the TotalAmt field anywhere where it will be available to the DataContext (and have access to the AirWayBill object)

Thanks again Viv,

I think I have managed to adjust the code to work in my application.