dialog in a docking pane

Hello,

What is the correct way of embedding a dialog in a docking pane?

I create the dialog in
LRESULT CMainFrame::OnDockingPaneNotify(WPARAM wParam, LPARAM lParam)

using this code:
case IDS_PANE_PICS:
 
 if (!m_wndDlgPics->GetSafeHwnd())
 {
  UINT li_template = IDD_DLG_PIC;
  m_wndDlgPics->Create(li_template);
 }
 pPane->Attach(m_wndDlgPics);
 break;

On application end I am getting assertion

wincore.cpp line (2655)
I am using VS 6.0

Thank you
Vaclav

fixed by changing dlg properties

style: from popup to child
border: from none to resizing