double document merge using keys

Is it possible to "key" on two values during a document merge? Let me
explain.

I have document that includes lesson name and the page range of the lesson:

Writing with Power
Pages 512

Collaborating Through the Writing Process
Pages 1332

I have transformed the information into the following xml:

<chapter>
       <Chapterlesson code="6.1.1">
         <ch>1</ch>
         <lesson>Writing with Power </lesson>
         <startNum>5</startNum>
         <endNum>12</endNum>
      </Chapterlesson>
      <Chapterlesson code="6.1.2">
         <ch>1</ch>
         <lesson>Collaborating Through the Writing Process </lesson>
         <startNum>13</startNum>
         <endNum>32</endNum>
      </Chapterlesson>
...
</chapter>

I have a set of standards that need to be aligned with each lesson. The
standards are coded to the page, not the lesson. Here is a snippet of the
current xml of standardDoc.xml:

<standards>
   <stand startNum="5" endNum="5">19.A.4</stand>
   <stand startNum="11" endNum="11">14.D.2</stand>
   <stand startNum="11" endNum="11">14.D.3</stand>
   <stand startNum="13" endNum="14">14.A.2</stand>
   <stand startNum="15" endNum="15">14.A.1</stand>
   <stand startNum="16" endNum="16">14.A.1</stand>
....
</standards>

The following stylesheet works as far as it goes. It only captures the
standards that match the start page of the lesson. What I need is way to
address standards with startNum >= $localStart and <= $localEnd. Is there a
way to do this using keys?

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

    <xsl:variable name="stand2page" select="document('stand2page.xml')"/>
    <xsl:key name="standPage" match="stand" use="@startNum"/>


<xsl:template match="Chapterlesson">
        <xsl:copy>
            <xsl:copy-of select="@*"/>
            <xsl:apply-templates/>
            <xsl:variable name="localStart" select="startNum"/>
            <xsl:variable name="localEnd" select="endNum"/>
            <xsl:for-each select="$stand2page">
                <stand><xsl:copy-of select="key('standPage',
$localStart)"/></stand>
            </xsl:for-each>
        </xsl:copy>
    </xsl:template>