Custom CCK field type - Inventory

I need a field, and I will pay to have it programmed. It is a field that will have general utility to Drupal and CCK, and thus will be contributed as a Drupal project.

Inventory field

I need a generic inventory field. It will let me specify which things I have in stock and how many. It will know how to print a summary of the inventory. It will take the list of things that can be in stock either from a list entered in the configuration of the field or from a PHP callback. In this respect it is much like a text field with a select widget; for a text field with a select widget you can specify a list in the Allowed values or specify a PHP snippet that fetches the list (allowing integration with dedicated modules for the purpose). The place where the inventory field differs from a text field is in the counting of the items. Each of the items in the list must be able to have a count (the number in inventory).

Here's a bit what the interface would look like:

Please respond with questions or suggestions about the functionality to this post. Please contact me via my contact form if you are interested in implementing this. Send me your qualifications (ie prior CCK work) and your bid.