Question for n-layer solution

Hello

I'm trying to make a simple program for road pavement design, in which the result of the first computation step is used for the second step, second to third, thir to fourth and so on.

As attached is a sheet which shows what the program should do for 4 layered system,

but I would like to make the program to work for n-layers.

My tries are probably far from a working solution, so therefore I ask for help.