Causes the host to enable or disable its main window as well as any modeless dialog boxes.
HRESULT EnableModeless( BOOL fEnable // enable flag );
[in] Flag that, if TRUE, enables the main window and modeless dialogs or, if FALSE, disables them.
Returns S_OK if successful, or E_FAIL if an error occurred.
This method is identical to the IOleInPlaceFrame::EnableModeless method.
Calls to this method can be nested.