the changes should be done on the same tree instead of generating a new
tree
That's not how XSLT is defined to work.
I'm afraid the right answer would be to use an XPath engine to implement
your own transform-in-place language.
______________________________________
Joe Kesselman, IBM Next-Generation Web Technologies: XML, XSL and more.
"The world changed profoundly and unpredictably the day Tim Berners Lee
got bitten by a radioactive spider." -- Rafe Culpin, in r.m.filk
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list