发送两次消息模拟按下按钮，第二次没有响应，请问怎么搞

PostMessageW(m_hWnd,WM_COMMAND,MAKEWPARAM(IDC_OpenClose,BN_CLICKED),(LPARAM)GetDlgItem(IDC_OpenClose)->m_hWnd);//发送消息模拟点击按钮
m_BaudRate.SetCurSel(m_BaudRate.FindString(0,"57600"));//调整参数
PostMessageW(m_hWnd,WM_COMMAND,MAKEWPARAM(IDC_OpenClose,BN_CLICKED),(LPARAM)GetDlgItem(IDC_OpenClose)->m_hWnd);再次发送消息，无响应