Dynamic XSL Sorting - Is there a way like this?

Ok, I am fairly new to XSL transformations but up until now I have been able to get everything I wanted out of it.  Now I am stumped on the sort.

First, let me give you a sample XML.
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<?xml version="1.0"?>
<HRISReport SponsorKey="1160" StartDate="01/01/2002" EndDate="07/17/2002" RptVersion="1.0">
	<Participants>
		<Participant SSN="000-00-0001">
			<LastName>Doe</LastName>
			<FirstName>John</FirstName>
			<Address Changed="N" International="N" AddressDateChange="">
				<Address1>PO Box 999</Address1>
				<Address2/>
				<City>Somewhere</City>
				<State>TX</State>
				<Zip>99999</Zip>
				<Country/>
			</Address>
			<Plans>
				<Plan PlanName="099Test" PlanID="1111" Group="C7777" ID="00001">
					<ContributionRateChanges>
						<ContributionRateChange>
							<HighCompCode>H</HighCompCode>
							<ParticipationDate>06/18/1990</ParticipationDate>
							<RateEffectiveDate>05/15/2002</RateEffectiveDate>
							<RateChanges>
								<RateChange Type="K" Name="401(k) Salary Deferral">
									<OldAmount>0</OldAmount>
									<OldPercent>7.5</OldPercent>
									<NewAmount>0</NewAmount>
									<NewPercent>15</NewPercent>
								</RateChange>
							</RateChanges>
						</ContributionRateChange>
					</ContributionRateChanges>
				</Plan>
			</Plans>
		</Participant>
		<Participant SSN="000-00-0002">
			<LastName>Smith</LastName>
			<FirstName>Missy</FirstName>
			<Address Changed="N" International="N" AddressDateChange="">
				<Address1>PO Box 888</Address1>
				<Address2/>
				<City>Somewhere</City>
				<State>TX</State>
				<Zip>88888</Zip>
				<Country/>
			</Address>
			<Plans>
				<Plan PlanName="099Test" PlanID="1111" Group="A7777" ID="00002">
					<ContributionRateChanges>
						<ContributionRateChange>
							<HighCompCode/>
							<ParticipationDate>10/02/2000</ParticipationDate>
							<RateEffectiveDate>03/22/2002</RateEffectiveDate>
							<RateChanges>
								<RateChange Type="K" Name="401(k) Salary Deferral">
									<OldAmount>0</OldAmount>
									<OldPercent>15</OldPercent>
									<NewAmount>0</NewAmount>
									<NewPercent>15</NewPercent>
								</RateChange>
								<RateChange Type="C" Name="">
									<OldAmount>0</OldAmount>
									<OldPercent>0</OldPercent>
									<NewAmount>40</NewAmount>
									<NewPercent>0</NewPercent>
								</RateChange>
							</RateChanges>
						</ContributionRateChange>
					</ContributionRateChanges>
				</Plan>
			</Plans>
		</Participant>
		<Participant SSN="000-00-0003">
			<LastName>Baker</LastName>
			<FirstName>Fred</FirstName>
			<Address Changed="N" International="N" AddressDateChange="">
				<Address1>PO Box 777</Address1>
				<Address2/>
				<City>Somewhere</City>
				<State>TX</State>
				<Zip>77777</Zip>
				<Country/>
			</Address>
			<Plans>
				<Plan PlanName="099Test" PlanID="1111" Group="A6666" ID="00003">
					<ContributionRateChanges>
						<ContributionRateChange>
							<HighCompCode/>
							<ParticipationDate>10/01/1997</ParticipationDate>
							<RateEffectiveDate>02/28/2002</RateEffectiveDate>
							<RateChanges>
								<RateChange Type="K" Name="401(k) Salary Deferral">
									<OldAmount>0</OldAmount>
									<OldPercent>7.5</OldPercent>
									<NewAmount>0</NewAmount>
									<NewPercent>15</NewPercent>
								</RateChange>
							</RateChanges>
						</ContributionRateChange>
					</ContributionRateChanges>
				</Plan>
			</Plans>
		</Participant>
	</Participants>
</HRISReport>

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Ok, now the XSL code to tranform this structure into a pretty HTML table:

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

<xsl:output method="html" encoding="UTF-8"/>
<xsl:param name="sortBy" select="'Name'"/>

<xsl:template match="/">
	<!-- Count the rate changes to verify have records -->
 	<xsl:if test="count(HRISReport/Participants/Participant/Plans/Plan/ContributionRateChang
es/ContributionRateChange/RateChanges/RateChange) > 0">	
		<link rel='stylesheet' href='/stylesheet.css'/>
		<HTML>
		<HEAD>
		<TITLE>Deferral Pct Changes</TITLE>
		</HEAD>
			<BODY>
				<table class='datatable' cellspacing='1'>
					<tr>
						<td class='ttitle' colspan='13'>Deferral Pct Changes</td>
					</tr>
					<tr>
						<td class='theader' colspan='13'>
							From <xsl:value-of select="normalize-space(HRISReport/@StartDate)"/> - To <xsl:value-of select="normalize-space(HRISReport/@EndDate)"/>
						</td>
					</tr>
					<tr>
						<td class='theader'>SSN</td>
						<td class='theader'>Last Name</td>
						<td class='theader'>First Name</td>
						<td class='theader'>Participant Group</td>
						<td class='theader'>ID Code</td>
						<td class='theader'>HCE Code</td>
						<td class='theader'>Participation<br/>Date</td>
						<td class='theader'>Request Date</td>
						<td class='theader'>Contribution<br/>Acct</td>
						<td class='theader'>Old<br/>Percent</td>
						<td class='theader'>New<br/>Percent</td>
						<td class='theader'>Old<br/>Amount</td>
						<td class='theader'>New<br/>Amount</td>
					</tr>
					
						<xsl:for-each select="HRISReport/Participants/Participant/Plans/Plan/ContributionRateChanges/C
ontributionRateChange/RateChanges/RateChange">
							<xsl:sort select="@*[name(.)=$sortBy]"/>

							<tr>
								<td class='tdatal'><xsl:value-of select="normalize-space(../../../../../../@SSN)"/></td>
								<td class='tdatal'><xsl:value-of select="normalize-space(../../../../../../LastName)"/></td>
								<td class='tdatal'><xsl:value-of select="normalize-space(../../../../../../FirstName)"/></td>
								<td class='tdatal'><xsl:value-of select="normalize-space(../../../../@Group)"/></td>
								<td class='tdatal'><xsl:value-of select="normalize-space(../../../../@ID)"/></td>
								<td class='tdatal'><xsl:value-of select="normalize-space(../../HighCompCode)"/></td>
								<td class='tdatal'><xsl:value-of select="normalize-space(../../ParticipationDate)"/></td>
								<td class='tdatal'><xsl:value-of select="normalize-space(../../RateEffectiveDate)"/></td>
								<td class="tdatal"><xsl:value-of select="normalize-space(@Name)"/></td>
								<td class="tdatar"><xsl:value-of select="normalize-space(format-number(OldPercent,'#0.00'))"/></td>
								<td class="tdatar"><xsl:value-of select="normalize-space(format-number(NewPercent,'#0.00'))"/></td>						
								<td class="tdatar"><xsl:value-of select="normalize-space(format-number(OldAmount,'###0.00'))"/></td>						
								<td class="tdatar"><xsl:value-of select="normalize-space(format-number(NewAmount,'###0.00'))"/></td>					
							</tr>
						</xsl:for-each>
				</table>
			</BODY>
		</HTML>
	</xsl:if>
</xsl:template>
</xsl:stylesheet>


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The issue is the sort.  If I use and hard code the following it works:
<xsl:for-each select="HRISReport/Participants/Participant/Plans/Plan/ContributionRateChanges/C
ontributionRateChange/RateChanges/RateChange">
	<xsl:sort select="../../../../../../LastName"/>
	<xsl:sort select="../../../../../../@SSN"/>
	
This sorts properly but if I try to pass in a parameter things start to fail.

The following works:
<xsl:param name="sortBy" select="'Name'"/>

works if the sort reads:
<xsl:sort select="@*[name(.)=$sortBy]"/>

<xsl:param name="sortBy" select="'OldPercent'"/>
 works if the sort reads:
<xsl:sort select="*[name(.)=$sortBy]"/>

But how do I sort off of LastName,FirstName or SSN as a parameter.  None of these fields appear to work unless I hardcode the sort.  I know this is a long post and I am terribly sorry but I have been fight this for a couple of days.  Thank you in advance.
_
    Robert A. Franklin
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