Anemone: Loop inside a Loop

Hello. I have a Question/Issue regarding Anemone and the loop function. Basically I want to do a loop inside a loop. In the picture we have two lines (A and B) divided into 100 sections. I also have two square surfaces, both located at the beginning of both lines. What I want to do is use the loop to move the surface down the lines point by point. Imagine if I just have line A. To solve the task I take the length of my point list -1 and use this as number of repeats. Input for D0 is -1 and inside the loop I use an Addition +1. I put the solution in the index of a list item from the point list and move the surface to that point and also put the solution of the addition in the loop end. If I start the loop now, my surface walks down the line until the end. Easy as that.

I am struggling with the second time. For every step I walk down on Line A, I want the surface on Line B walk the whole line to the end and back again. I tried a lot to use the fast loop inside the loop somehow to figure it out, but I didn’t found any solution. Is there anyone who could help or have an idea. Thank you so much. If you need any further information please tell me!

Attached the grasshopper file
Forum Loop.gh (27.3 KB)

is this a graphical thing, or you need also data to be actually looped?

Forum Loop_Re.gh (19.9 KB)