Susan:
Since no one has answered yet, I will say I don't think it can be done that way. You have a one-to-many relationship; each IC item has the possibility of multiple P/O lines that match the item. As an alternative approach, you could do a "linked" view where you click on the IC item and it shows the matching P/O lines in a separate view based on PO data. If your intent is on-screen inquiry, that would work.