Tree growth ring

Hello, I am a student in the Department of Architecture. I am working on a project using Grass Hopper in Rhino. I want to express the growth rings by using the curve and inserting the excel value of the growth time of the tree. But I don’t know how to use Grasshopper well.
So I ask for help to know even a simple algorithm. please.

As you provide nothing I don’t really understand why you need Excel!!
here a simple way using Grasshopper.
Here I choose a recursive way using plugin Anemone

Each time n points are chosen on the curve, the tangent is used to calculate a perpendicular direction using Cross Product with Z. The growth is chosen with a random component.
Points are moved and a new curve is generated. But is there are too many points very different growth the curve could self intersect.

tree concentric (11.3 KB)

here a version with a noise component

tree concentric growth (15.3 KB)