Is this legal xpath usage?

Hi there --
 
I have an apply-templates that is not working as expected. I 
want to select all PRODUCT elements with at least one TRACK 
that has a LAST_UPDATE element that is newer than the passed 
in 'trimDate' parameter.
 
I expect the external function jString:compareTo() to be 
called for each TRACK Element. It is called only once for the 
first TRACK. 
 
     <xsl:template match="/" >        
         <xsl:message>Filtering tracks earlier than 
 <xsl:value-of select="$trimDate" /></xsl:message>
         <PRODUCT_LIST PACKAGER="DWS" >
         <xsl:apply-templates 
 select="PRODUCT_LIST/PRODUCT[jString:compareTo($trimDate, 
 rioport:formatDate(./PRODUCT_DETAILS/TRACK/LAST_UPDATE)) &lt; 0]" />
         </PRODUCT_LIST>
     </xsl:template>
 
 
 Sample xml:
 
<PRODUCT_LIST>
 	<PRODUCT>
 		<DRM>
 			<DRM_ID>01</DRM_ID>
 			<DRM_NAME>Intertrust</DRM_NAME>
 		</DRM>
 		<CODEC>
 			<CODEC_ID>01</CODEC_ID>
 			<CODEC_NAME>AAC</CODEC_NAME>
 		</CODEC>
 		<CLEARINGHOUSE>
 			<CLEARINGHOUSE_ID>01</CLEARINGHOUSE_ID>
 			<CLEARINGHOUSE_NAME>DWS</CLEARINGHOUSE_NAME>
 		</CLEARINGHOUSE>
 		<PRODUCT_DETAILS PRODUCT_ID="BM1015204101" 
			 PRODUCT_TITLE="A Night On the Town" 
			 PRODUCT_ARTIST_DISPLAY_NAME="Bruce Hornsby &amp;
The Range" 
			 PRODUCT_ARTIST_SORT_NAME="Hornsby, Bruce &amp; The
Range" 
			 RELEASE_DATE="12/05/00" GENRE_TYPE="Rock">
 			<MEDIUM_TYPE_CD>F</MEDIUM_TYPE_CD>
 			<MEDIUM_TYPE_NAME>Full Play</MEDIUM_TYPE_NAME>
 			<SHIP_DATE>12/05/00</SHIP_DATE>
 			<DIGITAL_CUTOUT_DATE/>
 			<EXPLICIT_LYRIC>N</EXPLICIT_LYRIC>
 			<NUMBER_OF_TRACKS>11</NUMBER_OF_TRACKS>
 			<PRODUCT_PLAYTIME>55:07</PRODUCT_PLAYTIME>
 			<SELLING_PRICE>7.98</SELLING_PRICE>
 			
 			<TRACK SEQUENCE_NUMBER="01"  TRACK_TITLE="A Night On
The Town" 
				 TRACK_ARTIST_DISPLAY_NAME="Bruce Hornsby
&amp; The Range" 
				 TRACK_ARTIST_SORT_NAME="Hornsby, Bruce
&amp; The Range">
 				<TRACK_PLAYTIME>4:27</TRACK_PLAYTIME>
 				<FILENAME>1000001087</FILENAME>
 				<FILESIZE>4.13</FILESIZE>
 				<SAVE_AS_NAME>Bruce Hornsby  
 and  The Range_A Night On the Town_A Night On The Town</SAVE_AS_NAME>
 				<LAST_UPDATE>12/05/00</LAST_UPDATE>
 				
 			</TRACK>
 			<TRACK SEQUENCE_NUMBER="02"  TRACK_TITLE="Carry The
Water" 
				TRACK_ARTIST_DISPLAY_NAME="Bruce Hornsby
&amp; The Range" 
				TRACK_ARTIST_SORT_NAME="Hornsby, Bruce &amp;
The Range">
 				<TRACK_PLAYTIME>5:08</TRACK_PLAYTIME>
 				<FILENAME>1000001088</FILENAME>
 				<FILESIZE>4.81</FILESIZE>
 				<SAVE_AS_NAME>Bruce Hornsby  
 and  The Range_A Night On the Town_Carry The Water</SAVE_AS_NAME>
 				<LAST_UPDATE>12/05/00</LAST_UPDATE>
 			</TRACK>
 			<TRACK SEQUENCE_NUMBER="03" 
					 TRACK_TITLE="Fire On The Cross" 
					 TRACK_ARTIST_DISPLAY_NAME="Bruce
Hornsby &amp; The Range" 
					 TRACK_ARTIST_SORT_NAME="Hornsby,
Bruce &amp; The Range">
 				<TRACK_PLAYTIME>4:38</TRACK_PLAYTIME>
 				<FILENAME>1000001089</FILENAME>
 				<FILESIZE>4.32</FILESIZE>
 				<SAVE_AS_NAME>Bruce Hornsby  
 and  The Range_A Night On the Town_Fire On The Cross</SAVE_AS_NAME>
 				<LAST_UPDATE>12/05/00</LAST_UPDATE>
 			</TRACK>
 		</PRODUCT_DETAILS>
 	</PRODUCT>
 </PRODUCT_LIST>
 

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