CToolTipCtrl problem in WTL

i attach a tooltip to a listview, and each time the cursor move to a listview item , the tooltip will show some corespoding infomation.
the tooltip can really show listview line number indicting which row the cursor is moving on, but the tooltip won't disappear. 
i want the tooltip disappear after 2 second.

//create:
       CToolTipCtrl m_toolTip; //m_toolTip is a member variable in listview control

                //after listview created, create tooltip
        m_toolTip.Create(m_hWnd);//m_hWnd is the listview control
m_toolTip.Activate(TRUE);

m_toolTip.AddTool(m_hWnd);//m_hWnd is the listview control
m_toolTip.SetMaxTipWidth(260);

//mouse message
MESSAGE_HANDLER(WM_MOUSEMOVE, OnMouseMove)
LRESULT OnMouseMove(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)
{
int xPos = GET_X_LPARAM(lParam);  
int yPos = GET_Y_LPARAM(lParam);  
POINT pt = {xPos, yPos};  
int nItem = HitTest(pt, 0);//which line 
if (nItem >= 0)  
{  
CString s;
s.Format("item %d\nhello world", nItem);
m_toolTip.UpdateTipText(ATL::_U_STRINGorID(s), m_hWnd);  
m_toolTip.Activate(TRUE);  
}  
else
{
m_toolTip.Activate(FALSE);  
}  
m_toolTip.UpdateTipText("hello", m_hWnd);  

bHandled = FALSE; // Leave the message to next case  
return 0;  
}

//
MESSAGE_RANGE_HANDLER(WM_MOUSEFIRST,WM_MOUSELAST, OnMouse)

LRESULT OnMouse(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)  
{  
MSG msg = {m_hWnd, uMsg, wParam, lParam };  
if (m_toolTip.IsWindow())  
{  
m_toolTip.RelayEvent(&msg);  
}  
bHandled = FALSE;
return 0;
} 


thanks.


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