Up and down in folder hierarchy

I know how can I get up a folder with the .. but for the life of me I can't get down ( or across )

I got folder 1 and in it other two - A and B
from folder A I want to go to folder B,
I can't use the direct path as the parent folder will change a few times a day.

basically what I need is -

GO back to the parent folder, find another one in it( might be by name it will always the same ) and open it.

Any ideas?

If the name's always the same then you can use Go ..\B. Otherwise, have a look at Command: Go-Relative (go to next/prev sibling folder).