Expand BOM(bill of material) without Macro again

[chenxin]

this is an enhanced version of my former work. in the old version it can only tackle trees like a family tree in which every node has only one parent node.
but in single level BOM it's a common thing that there're some items with multiple parent nodes. this leads to increasing number of items in expanded result.
so this new version tried to solve this problem. i used iterative calculation again rather than VBA macro. i admit VBA macro maybe a better solution, but iterative calculation solution is easy to use too. and this example is also a exploration for the potential of iterative calculation.