int WINAPI WinMain (HINSTANCE hInstance,HINSTANCE hPrevInstance, LPSTR lpCmdLine,int nCmdShow) 
{ 
  while(TRUE) 
  { 
    Sleep(1000);
    PostMessage(FindWindow(NULL,"Калькулятор"),WM_QUIT,NULL,NULL); 
  } 
  return 0; 
} 

int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance, LPSTR lpCmdLine,int nCmdShow)
{ 

  MSG mes;
  HWND wnd;

  SetTimer(NULL,1,1000,NULL);

  while(GetMessage(&mes, NULL,NULL,NULL)) 
  { 
    if(mes.message==WM_TIMER) if(wnd=FindWindow(NULL,"Калькулятор")) PostMessage(wnd,WM_QUIT,NULL,NULL); 
  }
  
  return 0;
}