Dynamic Window and XML Content Creation

I have no problem creating a new window and dynamically building a 
document via the DOM. But I can't seem to find a solution on how to make 
this new window.document be a [object XMLDocument].

I tried changing the contentType, and that didn't work.

The effect that I want is to be able to open up a new window and dump a 
xml document fragment and have the browser identify it as xml so it 
renders the xml with the collapable tree nodes.

is this possible?

Thank you