correlate N-values to soil modulus, run a boussinesq stress distribution. Integrate Es/delta sigma V with respect to depth. Add 20 percent (long term aging effects).
Fattdad's is one option, the other one is to use the N-to-settlements Burland & Burbidge method, or some later variations of it (for example, Berardi & Lancellotta). Maybe I can find a spreadsheet, but the original is pretty straightforward to implement.
Berardi & Lancellotta is a pretty interesting iterative method, illustrated at page 66 of these presentations, I hope it's clear enough notwithstanding the Italian Language