xsl:variable

Hi

        Hopefully I'm just missing something silly here.  I need to 
declare a variable that will be used globally and possibly modify if a 
condition occurs. Yet I cannot discern the syntax to do so , any attempt 
seems to re-declare the variable.


The intent here is to increment the value pages if the condition is true. 
If I declare a new variable within the If to hold the value it will go out 
of scope which doesn't help me.
Ie.
Thanks in advance for any ideas.

<xsl:variable name="pages" select="( $totalitems - $leftover ) div 
$pagesize "/>
<xsl:if test="leftover &gt; 0 ">
        <xsl:variable name="$pages" select="$pages  =$pages +1"/>
</xsl:if>