Create specific type of relationship

Hi,

Great plug-in. I have no issues creating simple relationships but I am trying to create the following type of relationship and would appreciate a bit of direction on how to do it or if it is possible:

Relationship is: post to portfolio
Where to show relationship results: post
What to show: posts related to portfolio entries that are related to the specific post where the results are to be shown (single template).

Thanks in advance.
Chris