Basic Windows Programming question in VS2005

I created a win32 console application (without enable precompiled header option). And now my source code as this, there is two compiler errors.

// AFormattingMsgBox.cpp : Defines the entry point for the console application.
//
#include <windows.h>
#include "stdafx.h"


//int _tmain(int argc, _TCHAR* argv[])
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                     PSTR szCmdLine, int iCmdShow)
{
    int cxScreen, cyScreen;

    cxScreen = GetSystemMetrics(SM_CXSCREEN);
    cyScreen = GetSystemMetrics(SM_CYSCREEN);

    MessageBoxPrintf(TEXT("ScrnSize&quo开发者_StackOverflow社区t;), TEXT("The screen is %i pixels wide by %i pixels high."), cxScreen, cyScreen);

    return 0;
}


int CDECL MessageBoxPrintf(TCHAR * szCaption, TCHAR * szFormat, int x, int y)
{
    TCHAR szBuffer [1024];
    va_list pArgList;

    va_start(pArgList, szFormat);

    _vsntprintf(szBuffer, sizeof(szBuffer) / sizeof(TCHAR), 
                szFormat, pArgList);

    va_end(pArgList);

    return MessageBox(NULL, szBuffer, szCaption, 0);

}

Compiler Errors.

error C3861: 'MessageBoxPrintf': identifier not found

error C2365: 'MessageBoxPrintf' : redefinition; previous definition was 'formerly unknown identifier

How can I fix the errors. Thanks for your reading and replies.

---

Either put the function MessageBoxPrintf before the WinMain function or add a prototype before winMain. You add a prototype by entering the following line:

int CDECL MessageBoxPrintf(TCHAR * szCaption, TCHAR * szFormat, int x, int y);