Searching for the right tool

Hi everyone.

I'm looking for the right tool for a job. Hope someone can help. The
deal is this:

We have a large amount of data which is maintained by non-programmers.
This is validated and exported to a series of text files. These text
files are parsed into memory. Third parties are also able to modify
these text files.

I want to make life easier for these third parties, the "Modders" as
they're known in the trade, since they have no other interaction with
the company, and do not have access to the validators and exporters.
The text files carry with them no file format documentation, and I
think XML could partly solve this, particularly if we publish the
schemas to enable validation.

Currently, the data is created in MS Excel (the grid control is very
helpful), and a VBA script validates and exports it to plain text.
Excel will directly save as XML although with little structure on first
glance (could I use XSLT here?). The kind of tool I'm thinking of
would be a simple relational database which would take a set of schemas
and build the tables from that, allowing me to enter records and export
the tables as a set of coherent XML files.

Obviously, free is good. We're not really in to investing in new
technology.

Hope someone can help!

Cheers,
Guy

hatcat