need to pass a hidden field in a custompress template form

I’m creating a site for an art gallery. In customPress, I have it set up as:
Post Type: Piece of Art
Custom Attribute: Inventory ID
Custom Attribute: Artist name
etc…

I want to pass the Inventory ID (in a custom form I create on the custompress page) a the hidden field.

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I am looking to put a form on a customPress page. Basically, when someone finds a product they want, they would fill out a form. I would like to put one of the tags in the form as a hidden field.
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I am familiar with MySQL/HTML and am learning PHP. I know ColdFusion but that’s now as helpful as sanskrit