I have the following code that I use to validate certain cells that are editable:

        private void GrdMaint_OnRecordUpdating(object sender, RecordUpdatingEventArgs e)
        {
            //
            var cells = e.Record.Cells;
            var editFields = _Vm.EditColumns(_currentStep);
            var msg = string.Empty;
            var hasError = false;

            foreach (var item in cells)
            {
                var tmpMsg = string.Empty;
                
                if (!editFields.Contains(item.Field.Name)) continue;

                if (_Vm.PassesValidation(_currentStep, item.Field.Name, item.Value, out tmpMsg)) continue;

                hasError = true;
                msg += string.Format(" {0}",tmpMsg);
            }

            if (hasError)
            {
                System.Media.SystemSounds.Asterisk.Play();
                        
                lblValidationMessage.Content = msg;
                lblValidationMessage.Visibility = Visibility.Visible;

                GrdMaint.ExecuteCommand(DataPresenterCommands.StartEditMode);
               
                e.Action = RecordUpdatingAction.CancelUpdateDiscardChanges;
                e.Handled = true;                
            }
            else
            {
                e.Action = RecordUpdatingAction.ProceedWithUpdate;
                lblValidationMessage.Content = msg;
                lblValidationMessage.Visibility = Visibility.Collapsed;                
            }
        }

The problem I am having is that when the user enters in a wrong value the previous value is not retained nor is the field back into edit mode.  Am I doing this correctly?  Is there a better way to do cell validation?