Script and XSL codes

Hi all,
First, I am sorry if I post this message in the wrong
list.
Second, I have the following codes, it keeps giving me
the error: 'document.CaseManager.PrsnID.value' is null
or not an object.  PLease help!
Javascript:
-----------

<script language='javascript'>
	function casemanager()
		{
			var casemanager =  "../scripts/CaseManager.asp" +
"?PrsnID=" + document.CaseManager.PrsnID.value +
"&amp;SysID=" + document.CaseManager.SysID.value		
//alert(helppage)
			var props =
"dependent=yes,resizable=yes,height=400,width=350,status=no,toolbar=no,menubar=no,scrollbars=yes,top=10,left=300"
			helpwin =
window.open(casemanager,'CaseManager',props );
//,location=no
			helpwin.focus()
	}
</script>

xsl code:
---------

<xsl:template match="Service">
	<tr class="Grid">
		<xsl:attribute name="style">background-color:
<xsl:eval>fnIsOdd()</xsl:eval></xsl:attribute>
		<TD ALIGN="CENTER" nowrap=""
headers="Program"><xsl:value-of select="Program"
/></TD>
		<TD ALIGN="CENTER" nowrap=""
headers="Begin"><xsl:value-of select="Begin" /></TD>
		<TD ALIGN="CENTER" nowrap=""
headers="End"><xsl:value-of select="Servd_Thru"
/></TD>
		<TD ALIGN="CENTER" nowrap=""
headers="SiteName"><xsl:value-of select="Site_Name"
/></TD>
		<TD ALIGN="CENTER" nowrap=""
headers="County"><xsl:value-of select="Site_County"
/></TD>
		<TD ALIGN="CENTER" nowrap=""
headers="Phone"><xsl:value-of select="Site_Phone"
/></TD>
		<TD ALIGN="CENTER" nowrap="" headers="CaseManager">
			<form name="CaseManager" action="" method="post">
				<input type="hidden" name="PrsnID">
					<xsl:attribute name="value"><xsl:value-of
select="//Client/PrsnID" /></xsl:attribute>
				</input>
				<input type="hidden" name="SysID">
					<xsl:attribute name="value"><xsl:value-of
select="//Client/SysID" /></xsl:attribute>
				</input>
				<input type="button" value="Case Manager" 
onClick="casemanager();"></input>
			</form>
		</TD>
	</tr>
</xsl:template>

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