[Plugin: Developer's Custom Fields] Help with advanced options type

Hi guys, wondering if you had any pointers on the follow…

I’m wanting to data other than posts to dynamically populate an options field for a certain post type.

The data comes from a form and is stored in the same database as the site.

eg. New client fills in form and then that client is selectable when creating a new post. I then want to output a few details about that client along with the post.

Not sure if that makes sense, but I could do with some pointers please.

http://wordpress.org/extend/plugins/developers-custom-fields/