CodeBlocks files : .h .cpp main

Hi bit-pal ,
sono di nuovo qui, non perché sia pigro, ma perché quando non se ne viene a capo ....
Ambiente : CodeBlocks + minGW + Win32 + C++
Ho copiato il programmino sulla gestione della posizione del mouse che Rubik (generosamente) mi ha inviato.
Tutto OK finché resta file unico. Quando cerco di suddividerlo nei tre files canonici : .h .cpp main succede :

error : ld returned exit status

da ricerche fatte, sembra legato alla funzione main (). Di seguito i tre files fatti : .h .cpp main

#ifndef MY_H_INCLUDED
#define MY_H_INCLUDED

#if defined(UNICODE) && !defined(_UNICODE)
    #define _UNICODE
#elif defined(_UNICODE) && !defined(UNICODE)
    #define UNICODE
#endif

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>

const char *Name = "Coordinate mouse";
const char *Prog =   "Coordinate mouse";
const DWORD Win = WS_OVERLAPPEDWINDOW;
const WORD Wwin = 800;
const WORD Hwin = 600;

BOOL Register_Class ( HINSTANCE hIst );
BOOL Create_Window ( HINSTANCE hIst, int show );
void Show_PAINT ( HWND hWnd, char Text[20] );
void Error ( const char *msg, HWND hWnd );

#endif  // MY_H_INCLUDED

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <My.h>

LRESULT CALLBACK WndProc ( HWND hWnd, UINT msg, WPARAM wPar, LPARAM lPar ) {
	switch ( msg ) {
		case WM_LBUTTONDOWN:    InvalidateRect ( hWnd, NULL, TRUE );
			Show_PAINT( hWnd, "L_BUTTON\0" ); 	break;
		case WM_RBUTTONDOWN:    InvalidateRect ( hWnd, NULL, TRUE );
			Show_PAINT( hWnd, "R_BUTTON\0" ); 	break;
		case WM_MBUTTONDOWN:    InvalidateRect ( hWnd, NULL, TRUE );
			Show_PAINT( hWnd, "M_BUTTON\0" ); 	break;
		case WM_MOUSEWHEEL:     InvalidateRect ( hWnd, NULL, TRUE );
			Show_PAINT( hWnd, "WEEL\0" ); 		break;
		case WM_KEYDOWN:        InvalidateRect ( hWnd, NULL, TRUE );
			Show_PAINT( hWnd, "KEYBOARD\0" ); 	break;
		case WM_MOUSEMOVE:      InvalidateRect ( hWnd, NULL, TRUE );
			Show_PAINT( hWnd, "MOVE\0" );
			Sleep(50); 	                        break;
		case WM_SIZE:           InvalidateRect ( hWnd, NULL, TRUE );
			Show_PAINT ( hWnd, "SIZE\0" );
			Sleep(1); 	                        break;
		case WM_CLOSE: 	PostQuitMessage ( 0 ); 	break;
		default: return DefWindowProc ( hWnd, msg, wPar, lPar );   }
	return 0; }

BOOL Register_Class ( HINSTANCE hIst ) {
	WNDCLASS wc = {  0  };
	wc.lpfnWndProc = WndProc;
	wc.hInstance = hIst;
	wc.hCursor = LoadCursor ( NULL, IDC_ARROW );
	wc.hbrBackground = (HBRUSH)GetStockObject ( GRAY_BRUSH );
	wc.lpszClassName = Name;
	return RegisterClass ( &wc ) != 0; }

BOOL Create_Window ( HINSTANCE hIst, int mostra ) {
	RECT  r = { 0,0,Wwin,Hwin };
	AdjustWindowRect ( &r, Win, FALSE );
	OffsetRect ( &r,-r.left+10,-r.top+10 );
	HWND hWnd = CreateWindow (Name,Prog,Win,r.left,r.top,r.right-r.left,r.bottom-r.top,0,0,hIst,NULL );
	if ( hWnd != NULL ) ShowWindow ( hWnd, mostra );
	return hWnd != NULL;  }

void Show_PAINT ( HWND hWnd, char Text[10] ) {
	POINT pCoor;
	GetCursorPos (&pCoor);
	int x=pCoor.x;
	int y=pCoor.y;
	ScreenToClient (hWnd, &pCoor);
	PAINTSTRUCT ps;
	HDC hdc = BeginPaint (	hWnd, &ps );
	RECT r;
	char buff[128];
	GetClientRect ( hWnd, &r );
	wsprintf ( buff,"Finestra %d x %d\n\nPosWin %d x %d\n\nPosDesk %d x %d\n\n%s",r.right, r.bottom, pCoor.x, pCoor.y, x, y, Text );
	InflateRect ( &r, -7, -7 );
	DrawText ( 	hdc, buff, -1, &r, DT_EXPANDTABS );
	EndPaint ( 	hWnd, &ps );   }

void Error  ( const char *msg, HWND hWnd ) {MessageBox ( hWnd, msg, Prog, MB_ICONERROR );  }

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <My.h>

int WINAPI WinMain ( HINSTANCE hIst, HINSTANCE hPrevInst, LPSTR cmd, int show ) {
	MSG msg = { 0 };
	if   ( !Register_Class( hIst ) ) 		{ Error ( "Classe non registrata. ", NULL ); 	return 0; }
	if   ( !Create_Window( hIst, show ) )   { Error ( "Finestra non creata. ",    NULL ); 	return 0; }
	BOOL  msgOK ;
	while (( msgOK = GetMessage ( &msg, NULL,0,0 ) != 0 )) {
		if  ( msgOK ==  -1 )  {	      }		// codice per gestire l’errore
		else  {
			TranslateMessage(&msg);
			DispatchMessage( &msg ); }  }
	return 0; }

Dove sbaglio ? Grazie