Sorting imported data in lookup criteria

I have a form called CLIENTS and a form called VENDORS.

For a field (Photographer) in CLIENTS, I used the lookup feature to import a list (Company) in Vendors.

The items in company are labeled with "type" like "photo"

What script do I put in criteria box to restrict the data to only show the companies with "type" field being "photo"

I've tried using

<picklist fieldname>
(
type = picklist
values = <form name>[criteria].<fieldname to be imported from form name>
)

but got an error message.