how to get total string-length()

Hello all,
If I have the following snippet:

<fo:block margin-right="{concat(NNN*1.5),'mm')}">
--------------------------------^^^
   <xsl:call-template name="process-nodes"/>
   <xsl:if test="not(@no-pg-num)">
       <fo:leader leader-pattern="dots" leader-pattern-width="2.0mm"
leader-alignment="reference-area"/>
   </xsl:if>
   <xsl:for-each
select="document(concat($libname,'/index.xml'))//index/index-term[@id =
$primary]">
      <xsl:value-of select="."/><xsl:if test="position() !=
last()">,&nbsp;</xsl:if>
   </xsl:for-each>
</fo:block>

In the for-each line I grab each index-term that has an id that matches the
value in $primary.  Thus I could have a line like
   the index entry..........123, 234, 345

What I want to be able to do is, using the example in the line above,
calculate the number of characters in "123, 234, 345" and be able to insert
it in the NNN location in the block margin-right location.  Obviously I need
to figure this out outside/before the block, but howto, that's the question.
I'm almost embarrassed to ask, since this looks like now that it's written
down, like some kind of FAQ.

thanks for help,
   Matthew L. Avizinis <mailto:mla@xxxxxxxxx>
Gleim Publications, Inc.
   4201 NW 95th Blvd.
 Gainesville, FL 32606
(352)-375-0772
      www.gleim.com <http://www.gleim.com>


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