draw bitmap on Explorer-Style Custom Templates

Env: WindowsXP, VC++6.00

I am trying to preview a bitmap file by using Explorer-Style Custom
Templates and GetOpenFileName(). The following is what I did:

(1)make a dlg with ID=IDD_DLG_PREVIEW, style
=WS_CHILD|WS_CLIPSIBLINGS|DS_3DLOOK|DS_CONTROL

(2)put a picture(ID=IDC_STATIC1) with bitmap type on the dlg

(3)define OPENFILENAME ofn as follows,
ofn.lpTemplateName = MAKEINTRESOURCE(IDD_DLG_PREVIEW);
ofn.Flags |=
OFN_FILEMUSTEXIST|OFN_ENABLESIZING|OFN_ENABLETEMPLATE|OFN_ENABLEHOOK;
ofn.lpfnHook =
(LPOFNHOOKPROC)MakeProcInstance((FARPROC)GetOpenFileNameHook,
AfxGetApp()->m_hInstance);

(4)draw bitmap inside GetOpenFileNameHook() as follows,
UINT_PTR CALLBACK GetOpenFileNameHook( HWND hwnd, UINT msg, WPARAM wParam,
LPARAM lParam)
{
 switch (msg)
 {
  case WM_NOTIFY:
   LPOFNOTIFY lpOfNotify = (LPOFNOTIFY)lParam;
            if( lpOfNotify->hdr.code == CDN_SELCHANGE )
    if (IsItBitmapFile(FullPath))
    {
        HWND hStatic1 = GetDlgItem(hwnd, IDC_STATIC1);
        HDC hDC = ::GetDC(hStatic1);
        BitBlt(hDC, 0, 0, cx, cy, hdcImage, 0, 0, SRCCOPY);
    }
}

With the method above, the bitmap can be showed. However, the bitmap will be
rubbed if we un-activate the app and re-avtivate it.

Then, I make a class CPreviewDlg(IDD = IDD_DLG_PREVIEW) by ClassZiward. And
fix GetOpenFileNameHook() as follows,
UINT_PTR CALLBACK GetOpenFileNameHook( HWND hwnd, UINT msg, WPARAM wParam,
LPARAM lParam)
{
 switch (msg)
 {
  case WM_NOTIFY:
   LPOFNOTIFY lpOfNotify = (LPOFNOTIFY)lParam;
            if( lpOfNotify->hdr.code == CDN_SELCHANGE )
    if (IsItBitmapFile(FullPath))
    {
        InvalidateRect(hwnd, NULL, TRUE);
    }
}
And put a break at void CPreviewDlg::OnPaint().
But I find CPreviewDlg::OnPaint() is not called.
I don't know how to solve the problem.

TIA
ou