Cancel or suspend AfterCellUpdate method in grid

 Sorry for the duplicate post, I originally put this in the general questions, then noticed this forum which is more appropriate.

My main question is this... is there a way to "Cancel" or "Suspend" the grid so when I update a column the "AfterCellUpdate" method will not be called? 

I have a windows ultragrid (using 2007 V1), and I have logic in the "AfterCellUpdate" method that is causing me headaches!

Inside the method, I call another method that is outside this UI project.  When a user changes the value of the "Destination", "Origination" or "Loading Time" column, I have to call a method to calculate an "Arrival Time".

Example   The Loading Time column in a row is set to 4:00 PM the Origination column is New York and the Destination column is Atlanta.

The user changes the Loading Time to 3:00, and the Origination column to Minneapolis. I need to call my outside method to recalculate the Arrival Time...  what is happening is that I create a loop in my "AfterCellUpdate" method because I update the Loading Time column (because the date part of that column could change because of the other updates).

Thanks in advance!

Below is my method... I will BOLD the part that loops.

   string sourceProductionTypeID = string.Empty;
   string destinationProductionTypeID = string.Empty;

   if (activeCell != null)
   {
      try
      {
         switch (activeCell.Column.Key)
         {
            case "Origination":
            //update the TransportationGrid with data from the source SITE dropdown

                 activeCell.Row.Cells["SourceContactID"].Value = _dropDownGridRow.Cells["SiteContactID"].Value;

                 //call method to update the arrival time
                 marketLoadRecord = SetArrivalTime();
                 if (marketLoadRecord != null)
                 {
                     //right here is where it loops.  As soon as I set the ["LoadingTime"].Value , it fallse right back into the top of this method
                     TransportationGrid.Grid.ActiveRow.Cells["LoadingTime"].Value = marketLoadRecord.LoadingTime;
                     TransportationGrid.Grid.ActiveRow.Cells["ArrivalTime"].Value = marketLoadRecord.ArrivalTime;
                     TransportationGrid.Grid.ActiveRow.Cells["ArrivalDate"].Value = marketLoadRecord.ArrivalDate;                  
                 }

                 break;

          }
     }
     catch (Exception ex)
     {
          MessageBox.Show(ex.Message, "TransportationGrid_AfterCellUpdate Error", MessageBoxButtons.OK);
     }
   }
}