Calling a template before any other templates

Hi. I am trying to do something in XSLT 2.0 that requires that some of
my templates know what the result of other templates is (or will be).
I want to run a process that writes a file before any other templates
run and then be able to refer to that file during the rest of the
processing.

If I call a template from the first template like the following, can I
rely on it being completed before any other templates are applied? Is
there a reliable way to perform an operation before any templates are
applied?

<xsl:template match="/">
  <xsl:call-template name="this.template.must.be.first" />
  <xsl:apply-templates/>
</xsl:template>

Thanks for your help.

Peter Desjardins