Hwnd check fail :o?

Warum funktioniert dei Abfrage nicht ob das Fenster exestiert ?

Code:

wstring LPCWSTR_Windowname;
	HWND	HWND_Windowhwnd;
	bool	HWND_GetSucces=true;

	
	while(HWND_GetSucces)
	{
		cout << "Type in Window Name:";
		wcin >> LPCWSTR_Windowname;
		HWND_Windowhwnd = FindWindow(NULL,LPCWSTR_Windowname.c_str());
		HWND_Windowhwnd = GetWindow(HWND_Windowhwnd, GW_CHILD);

		if (HWND_Windowhwnd != INVALID_HANDLE_VALUE)
		{
			HWND_GetSucces=false;
		}
		else
		{
			wcout << "Error:Window '"<< LPCWSTR_Windowname <<"'could not found!" << endl;
			Sleep(500);
		}
	}