TestLink

Is there a way to create custom fields that are specific to a test specification only and not to the test case? For example, a test specification I have connects to a piece of hardware running a specific build of software. I would like to track the HW version, type, and SW build on this piece of equipment (and other details), but I only need this info over the entire test specification/run and not on a per test case scenario (where I understand I can create custom fields).

Thanks for any help.