[jQuery] Interface drag/drop: Limiting number of items

[Michael Price]

Here's a tricky one (although it probably won't turn out that way in the 
end!)

I've got two unordered lists and I'm using Interface to allow items to 
be dragged between the two. However, if possible I'd like to limit the 
top list to only contain a maximum of 3 items, with any further items in 
the bottom list. If an item is dragged into the top list, any item 
outside the top 3 moves down into the bottom list.

I've honestly got no idea where to start with this - can anyone provide 
some tips?

Regards,
Michael Price