How to set a synchronized navigation between 2 Scrollboxes?

Hi everyone, i ran into a small problem while blueprinting my Menu UI. I try to explain it the best way possible (UE4-22):

i have 2 vertical scrollboxes next to each other. Both can contain an undefined amount of child elements (picked up Items etc.) and can scroll up or down when the elements exceed the the visible frame. The child elements can only be accessed with a gamepad focus navigation (no mouse).

I use an escape navigation rule, so the focus can toggle between the neighbouring elements of the 2 boxes when pressing left or right. This works fine, as long as there are always 2 elements on the same “height”. But when this is not the case, the focus does not escape. I did setup a custom navigation rule, that stores the element child number and jumps to the last element of the other scrollbox, when there is no neighbouring element. This works OK, but it gets screwed up as soon as one scrollbox has a scroll-offset.

Is there an “elegant” way to compare the scrollstatus/offset of 2 scrollboxes or to deal with this using navigation rules?

Green: how it works
Red: does not work
Orange: i try to achieve