[xsl] how to do i18n with parameter substitution

[George James <GeorgeJ@xxxxxxxxxxxxxxx>]

I have a template that does language substitution for text strings.  I want
to extend this to be able to pass in a variable number of parameter values
that get substituted into placeholder in each language string.

The current template looks something like this:

  <xsl:template name='i18n'>
    <xsl:param name='caption'/>
    <xsl:choose>
      <xsl:when
test='document("phrases.xml")/phrases/phrase/target[../@key=$caption and
lang($language)]'>
        <xsl:copy-of
select='document("phrases.xml")/phrases/phrase/target[../@key=$caption and
lang($language)]' />
      </xsl:when>
      <xsl:otherwise>
        <xsl:copy-of select='$caption' />
      </xsl:otherwise>
    </xsl:choose>
  </xsl:template>

I have a phrases.xml document that looks like this:

<phrase key='Client not on file'>
 <target xml:lang='en'>Client number <p1/> not on file. Priority:
<p2/></target>
 <target xml:lang='de'>Prioritdt: <p2/>. Klient Nr. <p1/> nicht auf
Akte.</target>
</phrase>

How can I extend my template so that will take as input something like the
following:

<caption key='Client not on file'>
 <p1 value='123456'/>
 <p2 value='99'/>
</caption>

and produce one of the following strings, depending on the language:
Client number 123456 not on file. Priority: 99
Prioritdt: 99. Klient Nr. 123456 nicht auf Akte.

Can anyone help me with this?
George