The client terminates a data link by posting a WM_DDE_UNADVISE message to the server, as shown in the following code fragment:
WinDdePostMsg(hwndServer, /* Handle of server */
hwndClient, /* Handle of client */
WM_DDE_UNADVISE, /* Message */
pddeStruct, /* Shared-memory pointer */
DDEPM_RETRY); /* Retry */