Problems with sorting in XSL

I don't know, if my problem is simple
for you guys but I think you are my
only hope.

I've created an xml-database for our
intranet with the names and adresses of
our employees.
Now I want to sort it by either the
first name or the surename.


It basically looks something like this:

<xsl:stylesheet xmlns:xsl="http://www.w3.org/TR/WD-xsl">
<xsl:template>
     <xsl:for-each select="employee/data" order-by="+ surename">

[...]
Now I just want to replace the ___order-by"+ surename"___
with ___order-by"+ firstname"___ , so the whole
database is sorted by their firstnames.

Does anybody know an answer ?!?

Thanks in advance.


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