Identify Disparate Tiers Within N Rows

I have 2 columns of data (A and B), each from a different source and using a different range of values. Each column of data hits a “tier” or “plateau” every so often where the value for at least the next 4, but no more than 20, rows does not change (up or down) by more than 3%. I want to find each case/ location where there is a plateau in column B that is up to and including 16 rows after the plateau in column A. Desired target is formula for Excel spreadsheet, with explanation of function steps.