重写backKeyPressEvent事件,该如何处理

重写backKeyPressEvent事件

if (!webBrowser1.Source.Equals("http://www.baidu.com"))
            {
                string newURL = "http://www.baidu.com";
                try
                {
                    newURL = sta.Pop().ToString();
                    newURL = sta.Pop().ToString();
                }

                catch { MessageBox.Show("error!"); }
                webBrowser1.Source = new Uri(newURL); 

            }