void cd_WaitMsg(MDDOOR *cd_msg);
   
   ---
   
   Purpose: support routine which sends door message and waits for reply.
   
   Result : none
   
   Usage  :     msg->mdd_command = 13;
                msg->mdd_data = 0;
                memset(msg->mdd_string,0,SLEN);                  
                memmove(msg->mdd_string,pstring,sizeof(pstring));
                
                cd_WaitMsg(msg);