查找QQ登录窗口句柄

 IntPtr maindHwnd =FindWindow(null, "QQ"); //获得QQ登陆框的句柄  
                    if (maindHwnd != IntPtr.Zero)
                    {
                        IntPtr childHwnd = FindWindowEx(maindHwnd, IntPtr.Zero, null, "QQEdit");   //获得按钮的句柄  
                        if (childHwnd != IntPtr.Zero)
                        {
                            //SendMessage(childHwnd, BM_CLICK, IntPtr.Zero, null);     //发送点击按钮的消息 
                            IntPtr childHwnd2 = FindWindowEx(maindHwnd, IntPtr.Zero, null, "登录");
                            if (childHwnd2 != IntPtr.Zero)
                            {
                                SendMessage(childHwnd2, BM_CLICK, IntPtr.Zero, null);     //发送点击按钮的消息 
                            }
                            else
                            {
                                MessageBox.Show("没有找到登录按钮");
                            }
                        }
                        else
                        {
                            MessageBox.Show("没有找到子窗口");
                        }
                    }
                    else
                    {
                        MessageBox.Show("没有找到窗口");
                    }   

问题：
现在只可以取到QQEdit窗口句柄
请问如何取到里面的登录按钮(从图中可以看到只到QQEdit，不知为何)？
或是如何直接取到QQEdit时发送回车消息？