关于打开外部程序并且发送一个按键消息 （转

void CProgcessDlg::OnBnClickedButton1()
{
si.cb = sizeof(STARTUPINFO);
si.lpReserved = NULL;
si.lpDesktop = NULL;
si.lpTitle = NULL;
si.dwFlags = 0;
si.cbReserved2 = 0;
si.lpReserved2 = NULL;
BOOL bres = CreateProcess(_T("C:\\WINDOWS\\system32\\notepad.exe"),NULL,NULL,NULL,false,
NORMAL_PRIORITY_CLASS,
NULL,NULL,&si,&pi);
if(bres==false)
{
MessageBox(_T("打开不成功"));
}
else
{
WaITForInputIdle(pi.hProcess,0);
//CloseHandle(pi.hThread);
//CloseHandle(pi.hProcess);
}

}
void CProgcessDlg::OnBnClickedButton2()
{
::SendMessage((HWND)pi.dwThreadId,WM_PASTE, 0, 0);//我想发送一个"粘帖",但是做不到
//如果我想发送一个"5"的按键,请问怎么做
}