Thank you for helping me with my issue.  While your answer does prevent editing it does it at the grid level which is too big a scope.  There are other fields that are still editable and I would need to intercept for every editable cell and make sure editing was turned on.

Here is how I accomplished what I needed.  I though that cancelling in the ActiveCellChanging event would work but canceling the CellEnteringEditMode seems to do the trick.

private void TimeTransferDataGrid_CellEnteringEditMode(object sender, BeginEditingCellEventArgs e)
 {
 // If logged in user is not the subject of the transfer do not allow them to edit these columns
  if (e.Cell != null && (e.Cell.Column.Key == "ReasonCode" || e.Cell.Column.Key == "ReasonDescription"))
            {
                if (MainPage.CurrentAppUser.EmpCode != e.Cell.Row.Cells["EvcCode"].Value.ToString())
                {
                    e.Cancel = true;
                }
                // If reject flag has been choosen do not allow entry
                if (e.Cell.Row.Cells["RejectTransfer"].Value.ToString() == "1" || e.Cell.Row.Cells["ApproveTransfer"].Value.ToString() == "0")
                {
                    e.Cancel = true;
                }
            }
 }

Hello drdonna,

I am really glad that you managed to resolve your issue. If you need any further assistance on the matter, please do not hesitate to ask.

I have something kind of related.  On a grid row if a user clicks "Accept" for a time transfer they are required to choose a reason code from a drop down combo box in the next cell to the Accept checkbox cell.  I don't want the user to be able to remove focus from the grid row until they also pick a reason code from the combo editor.  I have not been able to force the grid to stay on the row.  I see editing examples for a single field being a specific value but what about other required fields on the same grid row?

I get around this by using a Childwindow but would rather force the user to stay on a grid row until all required data has been entered.  Even though it is not an error until they try and move off the row without picking a value, I could set an error state on the row after "Accept" has been clicked even though they have not had a chance to pick a value yet?  Maybe this would keep the focus on the row until the value was chosen?

I have used the SelectedRowsCollectionChanged event and messed with the PeviouslySelectedItems and NewSelectedItems but cannot keep focus on the grid row that is not complete.  It puts the grid into a funky state where moving the cursor selects cells and rows that are hovered over by the cursor.  I may be able to create a sample when I have some time.  I am supposed to be doing testing this week and since I have a work around we will see if this is acceptable to the users.

Hello drdonna,

Thank you for getting back to me. If you have any further questions or concerns on this matter, please do not hesitate to ask.

Thanks for the ideas maybe the combination of the two will give me what I want.  I will give it a try and let you know.  At one point I had the AllowEdit scope at Row and changed it to Cell and maybe that change is the problem.