Написал, токо немного подругому выглядит, до ума доводи сам, как тебе надо:
xml:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<Entity>
<EntityID>3</EntityID>
</Entity>
<objects>
<object>
<EntityID>2</EntityID>
</object>
<object>
<EntityID>3</EntityID>
</object>
</objects>
</root>

xsl:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0"
xmlns:sch="http://www.ascc.net/xml/schematron">

<xsl:template match="/">
<xsl:apply-templates select="//objects/object"/>
</xsl:template>

<xsl:template match="object">
<xsl:message>zahel</xsl:message>
<xsl:text>
</xsl:text>
<xsl:value-of select="position()"/>)=<xsl:value-of select="EntityID/text()"/>;
<xsl:variable name="filter">
<xsl:apply-templates select="preceding-sibling::object" mode="inner">
<xsl:with-param name="foo" select="EntityID/text()"/>
</xsl:apply-templates>
</xsl:variable>
<xsl:choose>
<xsl:when test="current()/EntityID/text() != //Entity/EntityID/text()">не совпал </xsl:when>
<xsl:otherwise> совпал </xsl:otherwise>
</xsl:choose>
</xsl:template>

<xsl:template match="object" mode="inner">
<xsl:param name="foo"/>
<xsl:if test="$foo = //Entity/EntityID/text()">
<xsl:value-of select="position()"/>,
</xsl:if>
</xsl:template>
</xsl:stylesheet>

результат:

<?xml version="1.0" encoding="UTF-8"?>
1) =2;
не совпал
2) =3;
совпал