Filtering portal in join relationship
So I'm facing a rather tricky situation which I can't wrap my head around.
I have an Inventory table and an Orders table linked through a Join table. The orders table is also linked to a second occurrence of the inventory table in 2 relationships: a x relationship (orderID's to invID's) and an = relationship (global filter = category). This last set of relationships have enabled me to create a portal on the orders layout that lists all available inventory from which you can select what you want to add to your shopping cart. The inventory list in the portal can be sorted based on categories (hence the global filter = category relationship).
Next to this portal on the layout is an occurrence of the Join table that displays everything that has been added to the order. In other words the content of the shopping cart.
This has all worked flawlessly so all is fine and dandy. But...
What I want to do is add a filter that would allow me to filter the Join table that is on the same layout. The reason is maybe irrelevant but some items that are added to the cart are actually boxes that hold several other items. I want the boxes content to be added to the order which I can achieve easily BUT I don't want them listed in the Join portal (shopping cart) because they are irrelevant.
So what should I do? Pleeeeeeeeeease help me...