[xsl] two transformations consecutively with OpenOffice

Background: I'm programming an XSL 2.0 file to use as an export filter in
OpenOffice 2.x.
The XSL transforms the OpenDocument XML into my own Schema. 
Afterwards I would like to transform the result XML with the XSL of my Schema to
XHTML. 

Question: Is it possible (and how?) to get those two transformations into one
XSL file? (Since I can only use one XSL file as a filter in OOffice)

I guess it won't be possible to pass the result XML to another XSL file. I've
heard about node-sets but I'm not sure how to use them and if it's even
possible with the OOffice parser.

Thanks for the input