How to shift a item/object within a list/curve?

Hi all, I am trying to shift this object (green) along a curve (red). But I can’t figure out how to shift the start location of the domain? (18.5 KB)

Thanks in advance

Something like this? (22.6 KB)

Hi, thanks for getting back,

I was more thinking of having a script where you can shift the platform/tread (green) back and forth anywhere along the curve (red) and anything outside of the domain will become steps.

I had another go at it!

It’s far more complex than I first thought! And there are still a couple of things that could be solved better, however this seems to work. (57.2 KB)