奇怪的有关问题，折腾好久了。没有Messagebox就不显示按钮

// dllmain.cpp : 定义 DLL 应用程序的入口点。
#include "windows.h"
#include "stdafx.h"
#define _T TEXT

HWND hwnd;
HINSTANCE hIns;
HWND hwndButton = NULL;
HANDLE hThread;
HWND hwndDLG;


DWORD WINAPI FunProc(LPVOID lparamater)
{
    hwnd = FindWindow(NULL,_T("Warcraft III"));
    hIns   =   (HINSTANCE)GetWindowLong(hwnd,   GWL_HINSTANCE);
    hwndButton= CreateWindow(_T("Button"), _T("btn"), WS_VISIBLE|WS_CHILD, 5, 5, 80, 20,hwnd, NULL, GetModuleHandle(0), NULL);
    if(hwndButton == NULL)
    {
        MessageBox(hwnd,_T("shibai"),_T("shibai"),MB_OK);
    }
    ShowWindow(hwndButton,SW_RESTORE);
    return 0;
}

BOOL APIENTRY DllMain( HMODULE hModule,
    DWORD  ul_reason_for_call,
    LPVOID lpReserved
    )
{



    switch (ul_reason_for_call)
    {
    case DLL_PROCESS_ATTACH:
        {    
            hThread = CreateThread(NULL,0,FunProc,NULL,0,NULL);
        }

    case DLL_THREAD_ATTACH:

    case DLL_THREAD_DETACH:
    case DLL_PROCESS_DETACH:
        WaitForSingleObject(hThread,0);
    }
    return TRUE;
}

DWORD WINAPI FunProc(LPVOID lparamater)
{
    hwnd = FindWindow(NULL,_T("Warcraft III"));
    hIns   =   (HINSTANCE)GetWindowLong(hwnd,   GWL_HINSTANCE);
    hwndButton= CreateWindow(_T("Button"), _T("btn"), WS_VISIBLE|WS_CHILD, 5, 5, 80, 20,hwnd, NULL, GetModuleHandle(0), NULL);
    if(hwndButton == NULL)
    {
        MessageBox(hwnd,_T("shibai"),_T("shibai"),MB_OK);
    }
    ShowWindow(hwndButton,SW_RESTORE);
    //不增加MessageBox(hwnd,_T("shibai"),_T("shibai"),MB_OK);
    return 0;
}

hwnd = FindWindow(NULL,_T("Warcraft III"));
    hIns   =   (HINSTANCE)GetWindowLong(hwnd,   GWL_HINSTANCE);
    hwndButton= CreateWindow(_T("Button"), _T("btn"), WS_VISIBLE|WS_CHILD, 5, 5, 80, 20,hwnd, NULL, GetModuleHandle(0), NULL);
    if(hwndButton == NULL)
    {
        MessageBox(hwnd,_T("shibai"),_T("shibai"),MB_OK);
    }
    ShowWindow(hwndButton,SW_RESTORE);
    MessageBox(hwnd,_T("shibai"),_T("shibai"),MB_OK);//增加了
    return 0;