You can use Mechanical scripting interface to retrieve this data and then do the RMS error calculation. Or may be better to do with APDL commands in Post26. In Post26 you can use NSOL command to store temperature time history at a node. You can retrieve this data into an array parameter using VGET command. May be others on the forum have better idea of how to do within Mechanical.
You are navigating away from the AIS Discovery experience