I am sorry could you clarify you say ControlLogix 500, That doesn't exist it is either Control Logix which is 5000 OR RSLoix whic is the SLC500 and PLC 5 families.
on the 5000 series it is quite possible to do this and real easy.
On each of your Tags you edit them and place at the end a 1 or a...
Might think about this, If you plug in your MP3 player you get what output....ANALOG
to the headphones. what you need to read is the voltage or current whichever is attainable. then when it stops for say 2 seconds that is the change in song. just make sure when loading the MP3 player you edit...
Your best bet would be to control the temperature with PLC using a Thermocouple input whether this is a single input or a multi.
This brings in the resistance to a card that the PLC can read you do the logic to output a 4-20Ma output to your SCR then using a PID in the PLC you can attain great...