You can send a positive acknowledgment by posting a WM_DDE_ACK message with the DDE_FACK and DDE_FRESPONSE flags set in the status word of the shared-memory data structure. The following code fragment shows how to do so:

/*  Specify the status flags, when allocating shared memory */
pDDEdata->fstatus = DDE_FACK | DDE_FRESPONSE;
    .
    .
    .

/*  Post the message */
WinDdePostMsg(hwndDest,           /* Handle of destination  */
              hwndSource,         /* Handle of source       */
              WM_DDE_ACK,         /* Message                */
              pDDEdata,           /* Shared-memory pointer  */
              DDEPM_RETRY);       /* Retry                  */