thank you Chandoo - I've already discerned that I need to learn much more about formulas, and I think there's going to be a lot of vlookup and offset in my future - I'll spend some time with your example later today.
I have a large list of my daily readings (blood glucose, Blood Pressure, and weight) for monitoring my Type II diabetes. I have two charts associated with this data, a 13-month chart (current month and 12 previous months) and a one-month, showing daily readings, trend-lines and 30-day moving...