Price list items of selected inventory items

In my GP to CRM integration I have a map that selects inventory items to create as products in CRM. In the filter Scribe excludes items based on an item class. However, when the price list item map runs it cannot be limited and selects price list items for items that should be excluded. The system then errors when trying to add them to CRM as it cannot locate the product to relate it to.


I thought in the Scribe map I would be able to join onto the item table to say "select price list items for products that are in the following item classes". However a join is not permitted. 


Any ideas?