Storing Partial Sums

Hi,
I am trying to get the sum of all values in a for-each
loop. Is it possible to store the partial sums to find
the final result?

xsl is something like this :

<xsl:for-each  select
="Documents/Document[(_at_)Doc_No=$lastdoc]/People/Person">
                
<xsl:variable name="person" select="@Person_Id"/> 
<xsl:variable name="week"
select="count(/DocRoot/Documents/Document/People/Person[(_at_)Person_Id=$person])"/>


<xsl:value-of
select="format-number(sum(/DocRoot/Documents/Document/People/Person[(_at_)Person_Id=$person]/@Avg)
div  $week, '##.##')"/> 
</xsl:for-each>



For the above xsl snippet what I am  trying to do is
to get the sum of all   
"sum(/DocRoot/Documents/Document/People/Person[(_at_)Person_Id=$kisi]/@Avg)
div  $week "    values. I tried to write an XPath
expression to find the sum but couldn't success. So I
need to store the partial sums to find the result.

Any idea?


                
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