Dynamic stilesheet assignement

hi.

i'm trying to build a publishing system via the cocoon
server.

i have a number of XML datasheets and XSL
stylesheeets: how can i dynamically join them each
other ?
in other words, how can i dynamically change the
assignement 
<?xml-stylesheet type="text/xsl" href="mysheet.xsl"?>
in the XML file ?

thanks in advance to everyone.



=====
massimo cravero
mcravero@xxxxxxxxx


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