Return row number that matches two conditions: one arithmetic, one count/incidence

This seems like it should be simple, but I am STUCK! Please help me out.

I have a hierarchy. Each level of the hierarchy has a number. Each row has a "parent"-- the item under which the row is nested in the hierarchy. The hierarchy is dynamic, so the parent row identification needs to be dynamic as well.

In the attached document, there is a column describing the row member, its hierarchy number, the count of times that hierarchy number has appeared (the lowest level excluded). The formula needs to find the closest (i.e., highest incidence) row that is one level higher in the hierarchy. Might make more sense in the attached.

I feel like an idiot because I cannot figure it out.

BTW, I must use a formula, not VBA.

Not a class assignment. I'm 34, and I have a professional degree. I distilled the question down to the basics-- sorry if the clarity feels a bit like an assignment. If there's a forum standard for "proving" one's legitimacy, I'm happy to comply to the degree I can. The data is confidential, so I can't post that. I cannot use VBA because another group (offshore) is automating part of the sheet so I don't have access to it.

Thanks Andrew R! You're awesome!