C / C++ / MFC

struct FindHwndWithProcIdStruct{
	DWORD dwProcId;
	HWND hWnd;	// handle of window
};
HWND DoFindWindowWithProcId(DWORD dwProcessId)
{
	FindHwndWithProcIdStruct myProcIdStruct = { 0 };
	myProcIdStruct.dwProcId = dwProcessId;
	::EnumWindows(gfnEnumWindowProc, (LPARAM)&myProcIdStruct);
	return myProcIdStruct.hWnd;
}
BOOL CALLBACK gfnEnumWindowProc(HWND hWnd, LPARAM lParam)
{
	DWORD dwProcessId = 0L;
	DWORD dwThreadId = GetWindowThreadProcessId(hWnd, &dwProcessId);
	if (dwProcessId == ((FindHwndWidthProcIdStruct*)lParam)->dwProcId;
	{
	   ((FindHwndWidthProcIdStruct*)lParam)->hWnd = hWnd;
	   return FALSE;
	}
	return TRUE;
}