Context rule to detect children?

[Steve Rickaby]

There appears to be no context rule that can detect whether an element has children - {last} and {notlast} refers to siblings. This is giving me some headaches in controlling the vertical spacing in lists that include a run-on paragraph in the last list element: the {last} rule is obeyed, even though - from a visual point of view - the list element is not the last element in the list. (The design call for more space below the list than between list items.) 

Is there a solution to this, or do I have to completely revise my list formatting so that there is no need to detect whether or not an element is the last list element?
-- 
Steve