Thank you so much, Carim. You're an absolute star!
I can get this task completed now, and then learn more about Index and Match functions.
Coincidentally, I have a note to look at these functions, along with the new xlookup and xmatch, as prompted by Excel help. I've just been so busy with this project that I haven't been able to put any time aside for it yet. I currently use vlookups with embedded hlookups because the data set headers can vary. It's probably not the most efficient way.
Time to put aside a few hours for training!