Nested Sortable that prevents moving outside the hierarchy?

Nested Sortable that prevents moving outside the hierarchy?

Hello everyone,
 
I have just stumbled into the world of jQuery and so far it seems amazing. I cam across it looking for a way to drag and drop a sortable list. The thing is that I have a nested list but I do not want the items to move out of their heirarchy which seems to be the case with the plug-ins I've come across.
 
Can anyone help me? Can I use the built-in sortable library or do I need a plug-in (and if so, what should I use?)
 
Example:
 
1111111111
     AAA
     BBB
     CCC
2222222222
     DDD
     EEE
     FFF
3333333333
     GGG
     HHH
     III
 
So basically if I move the "1111111" block it should take the A-C nested list with it but I also should be able to sort the A-C items without moving them into the D-F list or the 1-3 parent list.
 
I hope this makes sense. Any help is greatly aprpeciated.