Traverse dependency tree downward and upward

I pull my hair for 2 days now trying to figure out how to walk the tree down and up.
Here's my challenge: http://www.sqlservercentral.com/Forums/Topic971432-1550-1.aspx

So far, I figured out:
from specific node, I can traverse up and down to build a SELECT query for each adjacent node. I hit the wall while going down tree what if a adjacent node has branch going upward...geez... Maybe I'm too deep into the weed and become blind sighted for anyting obvious here and there. I might need to sit back and look at the problem at the higher up... maybe it's not that complicated as i thought...well.