Suggestions: File Layout Editor

 I'd would like some suggestions on how to implement the actual bands,

 or groupings, editor GUI for a file export system I am busy with.

 Currently, I have a tree view on the left, explorer style, which lists

 as top level nodes all the Sections in an export, e.g. Customers,

 Clients, Customer Invoices etc. Then, under each section I have the

 data source queries for that section, and all record defintions, i.e.

 column collections, for that section. Now in the XML definition file,

 under the record definitions, I have groupings to one level, where

 each grouping may be on Invoice Number.

 Each grouping can have a header, emitted once before each group, body

 emitted for each item in the group, and a footer, emitted once after

 each group. Header, body, and footer can contain one or more lines

 that correspond to record definitions. I'm now looking for ideas on

 how to present the layout of these groupings to users for editing.