ComboBox раскрывающийся наверх

WNDPROC old_cbb_wndproc;
LRESULT APIENTRY cbb_new_wndproc( HWND, UINT, WPARAM, LPARAM );
__fastcall TForm1::TForm1( TComponent *Owner )
               : TForm( Owner )
{
    old_cbb_wndproc = ( WNDPROC )SetWindowLong( cbb1->Handle, GWL_WNDPROC, ( long )  cbb_new_wndproc );
}
LRESULT APIENTRY cbb_new_wndproc( HWND hwnd, UINT msg, WPARAM w_param, LPARAM l_param )
{
    switch ( msg )
    {
    case WM_LBUTTONDOWN:
        TComboBoxInfo info;
        RECT r, list_r;
        info.cbSize = sizeof( TComboBoxInfo );
 
        GetWindowRect( hwnd, &r );
        GetComboBoxInfo( hwnd, &info );
        SendMessage( hwnd, CB_SHOWDROPDOWN, 1, 0 );
        GetWindowRect( info.hwndList, &list_r );
        MoveWindow( info.hwndList,
            r.left,
            r.top - list_r.bottom + list_r.top,
            list_r.right - list_r.left,
            list_r.top - list_r.bottom,
            1 );
        break;
    default:
        old_cbb_wndproc( hwnd, msg, w_param, l_param );
    }
}
// ---------------------------------------------------------------------------
__fastcall TForm1::~TForm1( )
{
    SetWindowLong( cbb1->Handle, GWL_WNDPROC, ( long )old_cbb_wndproc );
}