<?xml version="1.0" encoding="UTF-8"?>
    <update-this>
    <document name="http://blah">
     <amount>015-39</amount>
    <shipping>US::Ground:0.00</shipping>
    <url>http://www.blah.com/my-spade-clothing-11176/487/878765?dn_hhe=mylist-_-nothing-_-nothing-_-nothing</url>
    <size>11.5 D</size>
    <price>100.00 USD</price>
    <stock>present in stock </stock>
    </document>
    </update-this>

<?xml version="1.0" encoding="UTF-8"?>
    <document name="http://blah">
    <amount>015-39</amount>
    <shipping>US::Ground:0.00</shipping>
    <url>http://www.blah.com/my-spade-clothing-11176/487/878765?dn_hhe=mylist-_-nothing-_-nothing-_-nothing</url>

    <size>11.5 D</size>
    <price>100.00 USD</price>
    <stock>present in stock </stock>
    <discounted_price>90 USD</discounted_price>
    <increased_price>110 USD</increased_price>
    <my_id>487</my_id>
    <set_id>878765</set_id>
    </document>

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output indent="yes"/>
    <xsl:strip-space elements="*"/>

    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>


    <xsl:template match="document">
        <xsl:variable name="price" select="substring-before(normalize-space(price),' ')"/>
        <xsl:variable name="currency" select="substring-after(normalize-space(price),' ')"/>
        <xsl:variable name="difference" select="number($price) * .10"/>

         <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
            <discounted_price><xsl:value-of select="concat(format-number($price - $difference,'#,###.00'),' ',$currency)"/></discounted_price>
            <increased_price><xsl:value-of select="concat(format-number($price + $difference,'#,###.00'),' ',$currency)"/></increased_price>

        </xsl:copy>


    </xsl:template>

 <xsl:template match="size_present | size_stock">
    <xsl:copy>
        <xsl:value-of select="translate(., ' ', '')"/>
    </xsl:copy>
    </xsl:template>
    </xsl:stylesheet>