Is Excel capable of this operation?

If 6 is below threshold then why are rows 2-34 given Label A since those are only 4 and then 98 to 273 are given Label B also with White value of 6. And then Label E is rows 432 - 479 where White starts at 51 and max of 56 and then very next value is also 51 but not included. So it seems you can have a ramp (sliding threshold?) AND 51 to 56 may/could be 53+/-5% but then that would be 50.35 (round to 50) and 55.65 (round to 56) but then the 50 just before the first 51 isn't included either. and then Label F and G and L and Q and R and T and U are each 0 in column 1 (certainly below threshold). and then Label J does NOT include a 43 just before it starts but DOES include a 40 at the end right after a 43. label K is too short. Label P is also only 23 long but at least that is really close to 24.
So back to my points above. You mention an 'attached graphic' but I can't find it and that may help explain a lot of this. You mention thresholds, minimum deviations, averaging, etc... but I don't see those values anywhere except the 5% deviation you mention. Patrick suggested using StDev instead of a 'flat' deviation and you seem to like that idea? I suspect some of these labels maybe to point out things like areas not to count or plateaus for Orange and not White and hence I suggested the 2 separate columns.
I'd love to sink my teeth into this but feel like I'm grabbing blind from the refrigerator drawer and just as likely to grab an onion as a I am to grab an apple.