[Extendflash] C level extensibility

[Alias]

Hi guys,

I'm currently working on a moderately complex xml validation project,
and I'm looking at various ways of validating xml documents to a
custom XML schema from within the flash IDE.

Now, originally I was planning to do this via a third party webservice
somewhere - however, I'm thinking about maybe a small command-line
validator would be more practical, and less prone to failure due to
network outages.

However - a couple of things bother me about this approach -

1) I've never done anything so low level before with flash, and don't
know how well defined everything is

and more importantly,

2) Would there be a way to make it cross platform? It would need to
work on macs. We could probably insist on OSX, if that's any help.

Does anyone have any experience with this? Is making stuff like this
cross platform pretty much out of the question, or could it be done in
Java perhaps?

Any input would be appreciated.
Cheers,
Alias