I have Xamgrid in when when the user edits value I am show a messagebox

If value >20 then it should show message that is value you entered is > 20 ok/cancel

Ok should restore value and cancel should bring back the whole value

What should be done so that cancel restores the original value?

In cell exited edit mode I have

if (e.Cell.Row.RowType == RowType.DataRow)
                {
                    if (null != e.Cell.Row.Data)
                    {
                        xxx data = e.Cell.Row.Data as xxx;
                        if(data.field1 > 20)
                        {
                            MessageBoxResult result = MessageBox.Show("adjust value by 20.OK/Cancel?",
                                "xxx", MessageBoxButton.OKCancel);

                            if (result == MessageBoxResult.Cancel)
                            {
                               
                            }
                        }
                    }
                }