If I need send a message for the users acc. to some expression the temperature , pressure ..etc
With an AC 800M controller you can create custom application alarm and events using the SimpleEventDetector and AlarmCondBasic function blocks/control modules of the AlarmEventLib
The operator workplace can typically be designed with a permanent alarm display, e.g. Alarm List, Alarm Line, Alarm Sequence Bar or Alarm Band at the top most area. An example of this was visible in my reply on the other thread you posted today.