Sortables - disable placement on a certain side of a sortable?

Sortables - disable placement on a certain side of a sortable?


I have a list of horizontal sortable objects, and some objects contain
siblings which are not sortable, but hide when it's parent is being
sorted, and reappear when it's done sorting. The problem is that the
parent sortable object can have another sortable object placed to
either the left or right of it, but since it has siblings (in this
case all to the right of the parent) it messes up the order of things.
So my question: is there a way to say "this item can't have something
placed to its right, but can to it's left?"
Thanks