fo:list-block problem

Hello specialists!

I have got the follwing template:

<xsl:template match="text">
<fo:list-block provisional-distance-between-starts="20mm">
  <fo:list-item>
   <fo:list-item-label end-indent="label-end()">
        <fo:block font-size="{$size}">
         <xsl:value-of select="number"/>
        </fo:block>
   </fo:list-item-label>
  <fo:list-item-body start-indent="body-start()">
        <fo:block font-size="{$size}">
         <xsl:value-of select="headline"/>
        </fo:block>
  </fo:list-item-body>
 </fo:list-item>
</fo:list-block>
</xsl:template>

The following output is generated by this template for example:

1.1.1.1.1            Headline of the text

Now to the problem:
When the number is too long the pdf generator (Antennahouse) breaks the line
- but i don't want to size the number column bigger because in most cases 20
mm between number and headline are enough! So is there a way to size the
space between number column and headline dynamically when the number text is
too long???

Or what would you suggest for this problem?

Thanks
Markus

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