This message is sent to IPF by the application to identify the communication object window to which the HM_INFORM and HM_QUERY_DDF_DATA messages will be sent. This message is not necessary if the communication object does not expect to receive either of these messages.

hwndparam1
    HWND   objcomhwnd        /*  Handle of the communication object window to be set. */

param2
    ULONG  ulReserved        /*  Reserved value, should be 0. */

returns
    HWND   hwndprevioushwnd  /*  The handle of the previous communication object window. */