Description: &This attribute specifies the name of a call-back reference if a user supplied script or application should be invoked in case of a status change. The configuration details of the call-back reference are located in the agent's call-back configuration file. This file contains an entry for each call-back reference detailing the path and name of the script/application to run, the arguments being passed to the script/application, the system account being used to execute the script/application, and whether the call-back should be invoked prior to a status change. A value for this attribute can only be supplied by a definition in a configuration set.