adjustable post-and-beam system

Hello there.

Iam pretty new here and still a Noob. After a couple of tutorials and google searches i decided to ask you guys.

I need to build a post-and-beam system, where i can manipulate the distance between the posts. even when i decide to change the overall frame of the whole construction (f.e length, size or geometry). I messed around with most of the divide components like Div Distance, Div Length, Div Distance + Reference. But in any of these cases, the posts are not perpendicular. For me thats not too surprising because the lenth of each curve wich builds the frame is different and the curves arent parallel. Is there a way to tell grasshopper to divide both curves in a way, that the points are perpendicular in the z axis?

I hope the attachment is helping you understand what I want to do.

hopefully I dont want to do smth wich isn't really doable, but i guess iam just not good enough to see the solution.

Thank you in advance