I am looking to display items in a collection fieldtype only if they contain the item in another fieldtype.

The scenario is, I have a collection of products and a collection of invoices and I'd like to show only the products that are NOT in the collection fieldtype of the invoices.

Example of how I expected it could be done:

    {{ relate:products scope="my_product" }}
        {{ collection:invoices scope="my_invoice" }}
                    {{ my_invoice:products as="invoice_product" }}
                        {{ if my_product:id == invoice_product:id }}
                            <h4>{{ my_product:title }}</h4>
                        {{ /if }}
                    {{ /my_invoice:products }}
        {{ /collection:invoices }}
    {{ /relate:artworks }}

I guess I expected collections to behave more like taxonomies...