Modifying ToolBar During Runtime

What I'm trying to do is have a combo box on the tool bar that I can some what destroy and create during runtime in order to switch styles between CBS_DROPDOWN and CBS_DROPDOWNLIST. 

Problem is:  After its changed, i have to make a mousemove inorder for the combo box to actually come up instead of a grey area. 

What I have inside of CMainFrame::OnCreateControl(LPCREATECONTROLSTRUCT lpCreateControl) for this works great on start up.  FYI:  I make a CXTPControlCustom and do lpCreateControl->pControl = pControlEntry.  I save a pointer to this CXTPControlCustom in my custom combo class.(call it m_pControlEntry)

Here is the code for how I change the combo box. for example from dropdown to dropdown list

//////////////////////////////////////////////////////////// /////////////////////////

 ModifyStyle(CBS_DROPDOWN, CBS_DROPDOWNLIST | WS_VSCROLL);
 
if (this == NULL)
  return FALSE;
 if (this->GetSafeHwnd() == NULL)
  return FALSE;
 CWnd* pParent = this->GetParent();
 if (pParent == NULL)
  return FALSE;
 DWORD dwStyle = this->GetStyle();
 DWORD dwStyleEx = this->GetExStyle();
 CRect rc;
 this->GetDroppedControlRect(&rc);
 pParent->ScreenToClient(&rc);
 UINT nID = this->GetDlgCtrlID();
 CFont* pFont = this->GetFont();
 CWnd* pWndAfter = this->GetNextWindow(GW_HWNDPREV);

 CComboBox comboNew;
 if (!comboNew.CreateEx(dwStyleEx, _T("COMBOBOX"), _T(""),
  dwStyle, rc, AfxGetMainWnd(), nID, lpParam))
  return FALSE;

    comboNew.ShowWindow(SW_HIDE);

    SetOwner(AfxGetMainWnd());

    comboNew.SetFont(pFont);
 this->DestroyWindow();
 HWND hWnd = comboNew.Detach();
 this->Attach(hWnd);

    if (m_pControlEntry)
    {
        m_pControlEntry->SetControl(this);
    }

//////////////////////////////////////////////////////////// ////////////////

So afterwards, theres a grey area until a little after i move my mouse, is there some kind of update i can call?  m_ComboBox for example is the name of the combobox.

I've tried m_ComboBox.RedrawWindow(), Invalidate(), Redraw(), SetVisible, and none of those will do it.

Tony