Thanks for the quick and thorough reply.
I'll test your code and post the results!
I have the results.
The graph did not show well because there are two bands at 0 and 100 but it looks like we are getting something. The 16 values running average of the derivative in particular seems to pick up nicely when the signal is increasing or decreasing or staying relatively steady.
I am attaching the spreadsheet itself so you can take a look.
Thanks for your help