I'm not sure of an excel spreadsheet here, but I've seen a graph that plots the proposed lessening impact of different severity late payments (30, 60, 90, 120) over time. I believe that member ABCD created the graph, so you could always PM him for it. Outside of that, I'm not sure of any other tool.
Keep in mind that such a chart really only works for 1 late payment. Once you are talking multiple late payments, diminishing returns often prevents much else from happening to a score. All that really matters is what your worst severity late is and how long ago that occurred.
For example, two people may have otherwise identical profiles outside of their payment history. Both have a 90 day late payment that's 6 months old. For one of these individuals, that's his only late payment. The other in addition to that single major negative has 5-6 other minor 30-day late payments from 4-6 years ago. These two individuals may very well possess nearly identical FICO scores, because the algorithm would be considering their most recent and most severe negative item most considerably, which would be the same for both.
