Combining two trees

Hello all.

If I have Document A (built from an XML source) with some child node "foo"
and Document B (built from a different XML source), is there a way for me to
replace the "foo" node in Document A with the entire Document B tree?

I tried to do this by creating a DocumentFragment from Document B and doing
a replaceNode() in Document A. I get an exception WRONG_DOCUMENT_ERR where
it tells me the node I'm inserting is from a different Document than the one
that created it.

Is there a way to do this?

Thanks in advance for any help.

Dan Noguerol