[flexcoders] Count of items in a list

[jmfillman]

I'm having difficulty in determining if a list has any items already in 
the list. For example, if a list already has 1 item, I want to set it's 
dropEnabled property to false, either when the item is added to the 
list or when the user attempts to drop a 2nd item. Also, if that item 
is removed from the list, I want to set dropEnabled to true.