I don't really follow your data structure, but I bet that previous_value could work for you.
does PREVIOUS_VALUE account for possible null values, and if so how should I revise my calculated field with it?
I went with the LOOKUP+ZN combo to enable the possibility to do a percentage comparison with not only the previous value but with a value that can be X entries away timewise (hence the [Count] parameter where I can change it from 1 to whatever I need).
thanks in advance for your feedback on this
Were you able to Overcome the issue , Can you post the solution here.