how to update with multiple outer joins

[VSB]

I have a manhole-pipe network. The pipes may be incoming or outgoing in reference to the manhole. The pipe table has two fields (FromNodeID and ToNodeID) to hold the manhole ID at each pipe end. What I want to do is establish two outer joins between the manholes and pipes (one each for incoming and outgoing pipes), then update a field in the manhole table with the concatenation of the pipes IDs (both incoming and outgoing). I created successfully the two 1-M relationships but Access won't allow me to even display the query, let alone update. Any ideas, please?

Thanks!