Called by the framework to retrieve the number of children belonging to this object.
Returns S_OK on success, a COM error code on failure. See Return Values in IAccessible::get_accChildCount in the Windows SDK.
This function is part of MFC's Active Accessibility support.
Override this function in your CWnd-derived class if you have nonwindowed user interface elements (other than windowless ActiveX controls, which MFC handles). Call the base class version and then add the nonwindowed child elements.
For more information, see IAccessible::get_accChildCount in the Windows SDK.