用WINEXEC调用一个可执行文件,如何判断执行完毕

用CreateProcess

PROCESS_INFORMATION pi;
STARTUPINFO si;
ZeroMemory(&si, sizeof(si));
si.cb = sizeof STARTUPINFO;
si.wShowWindow = SW_HIDE;
si.dwFlags = STARTF_USESHOWWINDOW | STARTF_USESTDHANDLES;
BOOL res = CreateProcess(
NULL,
_T("a.exe"), 
NULL,
NULL,
NULL,
NORMAL_PRIORITY_CLASS,
NULL,
NULL,
&si,
&pi);

if(res)
{
WaitForSingleObject(pi.hProcess, INFINITE);  
CloseHandle(pi.hProcess);
CloseHandle(pi.hThread);
}