C / C++ / MFC

Hi Dveleopers,
I have some problem regarding combo-box control. In one situation it give the list properly and in the other one it appears till the mouse is hold after that it get hides. If we click on arrow part of combo box it behaves properly, but if we click on the text part it give the list while mouse is in hold after that it get hide.

In 1st condition I have added almost 15 items and in other situation almost 500 items is being added.
The only difference between these items is that 1st one is CString and the 2nd one is char*.
Here the sel change of another combo based on that combo box ""m_chap"" ( in which I have problem is being populated ). pFnameMap is a structure and pFnameMap->fullName is a char*.

CString	szTemp;
m_nUserType = m_Rep.GetCurSel();

m_Chap.ResetContent();
if(m_nUserType != LB_ERR)
{
    m_Rep.GetLBText(m_nUserType, szTemp);
 
    if (szTemp.Find("Materia") >= 0)
    {
        FNAMEMAP1 *pFnameMap = NULL;
   
        for( int i=0;i& heApp.m_ChapterNameMap.GetCount();i++)
	{
	   if(APP->m_ChapterNameMap.Lookup((WORD)i,(void    near *&)pFnameMap))
	   {
	      if(stricmp(pFnameMap->repName, "Complete")==0)
	      {
		m_Chap.AddString(pFnameMap->fullName);
	      }
	   }
	 }
     }
     else
     {
	szQuery =  "Repertory = '" + szTemp + "'";
	m_pRsRepChaps->SetFilter(szQuery);
	while(!m_pRsRepChaps->IsEOF())
	{
	   m_pRsRepChaps->GetFieldValue("Chapter", szTemp);
	   if(m_Chap.FindStringExact(-1, szTemp)==LB_ERR)
	   {
	      m_Chap.AddString(szTemp);
	   }
	   m_pRsRepChaps->MoveNext();
	}
     }		
}

Combo box style is dropdown.

Thanks in advance.
Amrit Agrawal
Software Developer

	mouse_event( MOUSEEVENTF_LEFTDOWN, 0,0,0,NULL);
	mouse_event( MOUSEEVENTF_LEFTUP, 0,0,0,NULL);

	VOID mouse_event(          DWORD dwFlags,
    DWORD dx,
    DWORD dy,
    DWORD dwData,
    ULONG_PTR dwExtraInfo
);//how to use this funcation to move mouse to pt.x,pt.y???