WinAPI Funkcja typu MessageBox

#include <windows.h>

LRESULT CALLBACK WndProc( HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam );

int WindowHelp()
{
    WNDCLASSEX wc;
    wc.cbSize = sizeof( WNDCLASSEX );
    wc.style = 0;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = GetModuleHandle( NULL );
    wc.hIcon = LoadIcon( NULL, IDI_APPLICATION );
    wc.hCursor = LoadCursor( NULL, IDC_ARROW );
    wc.hbrBackground =( HBRUSH )( COLOR_WINDOW + 1 );
    wc.lpszMenuName = NULL;
    wc.lpszClassName = "Klasa Okienka";
    wc.hIconSm = LoadIcon( NULL, IDI_APPLICATION );
    RegisterClassEx( & wc );
   
    HWND hwnd = CreateWindowEx( WS_EX_CLIENTEDGE, "Klasa Okienka", "Oto okienko", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 240, 120, NULL, NULL, GetModuleHandle( NULL ), NULL );
   
    ShowWindow( hwnd, SW_SHOW );
    UpdateWindow( hwnd );
    MSG Komunikat;
    while( GetMessage( & Komunikat, NULL, 0, 0 ) )
    {
        TranslateMessage( & Komunikat );
        DispatchMessage( & Komunikat );
    }
    return Komunikat.wParam;
}

int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow )
{
    WindowHelp();
    WindowHelp();
    return 0;
}

LRESULT CALLBACK WndProc( HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
    if( msg == WM_CLOSE )
         DestroyWindow( hwnd );
    else if( msg == WM_DESTROY )
         PostQuitMessage( 0 );
    else return DefWindowProc( hwnd, msg, wParam, lParam );
   
    return 0;
}