xslt - How can I summarize nodes using calculation data from other nodes -

using xslt 1.0, how can summarize subnodes under given node while modifiyng content data set of nodes in elegant way? assume have xml:

<root>     <exchangerates>         <exchangerate>             <currencycode>usd</currencycode>             <rate>6.4</rate>         </exchangerate>         <exchangerate>             <currencycode>eur</currencycode>             <rate>8.44</rate>         </exchangerate>         <exchangerate>             <currencycode>sek</currencycode>             <rate>1</rate>         </exchangerate>     </exchangerates>     <prices>         <price>             <currency>sek</currency>             <amount>10000</amount>         </price>         <price>             <currency>eur</currency>             <amount>1000</amount>         </price>         <price>             <currency>usd</currency>             <amount>1000</amount>         </price>     </prices> </root> 

i want sum of amounts converted sek of exchangerates. result should be:

<suminsek>24840</suminsek> 

if didn't have convert amounts use xpath sum() function. is possible use function in case?

another possible solution without recursive calls exsl extension. make use of key definition form @softwarebear.

<?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/xsl/transform"         xmlns:exsl="http://exslt.org/common"         extension-element-prefixes="exsl">      <xsl:key name="rates" match="//exchangerate/rate" use="parent::*/child::currencycode/text()"/>      <xsl:template match="/" >         <xsl:apply-templates select="//prices"/>     </xsl:template>      <xsl:template match="prices">         <suminsek>             <xsl:variable name="price_sek">                 <xsl:apply-templates mode="sek" />             </xsl:variable>             <xsl:value-of select="sum(exsl:node-set($price_sek)//price_sek)"/>         </suminsek>     </xsl:template>      <xsl:template match="price" mode="sek">         <price_sek>             <xsl:value-of             select="number(amount) * number( key('rates', currency) )" />         </price_sek>     </xsl:template> </xsl:stylesheet> 

wiht output

<suminsek>24840</suminsek>