I think that is the case: flows will change quickly over time. What you suggest makes sense to me. I will do just that.
Last night I was reading some Arduino learning material that I downloaded. Very extense and very good. A lot more complete than the manual I got. This should help too.
Thank you very much for the suggestions. I hope I can make the sketch for the two interrupts myself. Will try to work more systematically.
Best,
OldBeaver 