The CDN_FOLDERCHANGE notification message is sent by an Explorer-style Open or Save As common dialog box when a new folder is opened. Your OFNHookProc hook procedure receives this message in the form of a WM_NOTIFY message.
CDN_FOLDERCHANGE lpon = (LPOFNOTIFY) lParam;
The OFNOTIFY structure contains an NMHDR structure whose code member indicates the CDN_FOLDERCHANGE notification code.
The return value is ignored.
The system sends this notification only if the dialog box was created using the OFN_EXPLORER value.
To get the path of the newly opened folder, the hook procedure can send the CDM_GETFOLDERPATH message to the dialog box.
CDM_GETFOLDERPATH, GetOpenFileName, GetSaveFileName, NMHDR, OFNHookProc, OFNOTIFY, WM_NOTIFY