Select Next or Previous folder

Hello.

Here's my problem:
I am in a folder. I go up one level and then I want to go one into the previous or next folder.
I want to do this with 2 buttons. One for "folder Up" and one for "folder Down".

Although this seems pretty simple, I cant seem to solve this. Can anybody help me?

Thanks,
Wilco.

I've written this, which I think does what you want:

Command: Go-Relative (go to next/prev sibling folder)

Thank you, Leo, for writing this. I didn't think I'd like it until I tried it. Comes in very handy.