[thelist] posting to xml

Here's the steps of what I'm trying to do (easiest to describe this
way):

1.  I POST a form with lots of hidden fields to another company's script
(can't use a GET.. it would be too long)
2.  The other company returns an xml page which I need to stuff into a
DOMDocument or xml Island

I'm currently using MSXML 3.0...  if I use the xmlhttp object, I can set
the method to POST, but how do I send along the hidden <input>'s?  Is
there another way?  

Once again, using GET isn't an option, and just displaying the XML
return with XSL isn't an option.

Thanks for any ideas!

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