Keeping track of a temporary window

I bring up a window which stays up for 3 seconds, after which it automatically closes. The mechanism for this is that I have a worker thread which sends WM_CLOSE message to this window after 3 seconds and the thread ends as well having done its job.

The problem is that I need to bring window up again based on user action but there is no good way how can I tell if this window is already up or not.

Code:

---

void CDemoDlg::ShowStatusWnd()
{
        m_pWnd = new CStatusWnd;
               
        // create and display
        m_pWnd->Create(m_pMainFrame);
        m_hwndSafeWnd = m_pWnd->GetSafeHwnd();
}

---

The CStatusWnd has the thread function which sends it WM_CLOSE

Code:

---

UINT CStatusWnd::EndStatusWnd(LPVOID pParam) // thead function
{
        CStatusWnd * wnd = (CStatusWnd *) pParam;
       
        Sleep(3000);
       
        ::PostMessage( wnd->m_hWnd, WM_CLOSE, 0, 0 );       
}

---

The problem is I keep track of CStatusWnd with m_pWnd pointer but how do I know [in ShowStatusWnd() function] that I have window up or it contains lefover values? Is there a way I can set to NULL when window is destroyed?

Another question with this is should I be deleting the C++ object in PostNcDestroy() handler like below?

Code:

---

void CStatusWnd::PostNcDestroy()
{
  CWnd::PostNcDestroy();
 
  delete this;
}

---