How can I prevent multiple appearances of the same record in a portal?

[Rapt Productions]

Hello, I'm trying to figure out a way to prevent a single record appearing more than once in a portal. I don't know how to work with the data in the portal fields since they aren't treated as part of the table I'm trying to affect.

In the attached file, I've got two tables, contact and company, with portals connecting them. I've set up a button to create a new record in the other layout (i.e. create a new contact from companies) or to go to an existing record. My problem is preventing the same record from showing up multiple times in either portal. I apologize if I'm not explaining very well, I'm a filemaker newb and I welcome all suggestions and feedback. Thanks for your time!

RaptClone12-9.fp7.zip

[pacific707]

your portal is based on the wrong table. edit your portal to show contacts not Contact_Companies and remove the checkbox allow creation of records via this relationship. You don't need it because you have a button to go this