[xsl] how to do the expression and count function correctly?

["Zoe Peng" <zoe@xxxxxxxxxxxx>]

Hi, 
Please help about the expression and count function. 

if item_service exist, I want to display item_service_svc_id; 
otherwise, I want to display the item_id. 

Results I want: 
Top Stories: 7009
News: 3.2


the problem I am facing is: It always displays item_id(3.1, 3.2) cuz 
$nService is always grate than 1 in this case. what should I do?? any 
function I can use?? Thanks. 
--Zoe

<!-- xml document -->
<?xml version="1.0"?>
<tm_user_device_menu statuscode="0" statusdesc="OK">
<user_device usr_id="user1"  />
<menu>
       <item item_id="3.1" item_title="Top Stories" >
            <item_service item_service_type="default" 
item_service_svc_id="1000" item_service_usr_svc_nam="Top Stories" />
       </item>
       <item item_id="3.2" item_title="News" >
              <item item_id="3.2.1" item_title="US" >
                <item_service item_service_type="default" 
item_service_svc_id="1001" item_service_usr_svc_nam="US" />
              </item>
              <item item_id="3.2.2" item_title="Americas" 
item_dsc="America" item_image_path="/images/news.gif">
                <item_service item_service_type="default" 
item_service_svc_id="1002" item_service_usr_svc_nam="Americas" />
              </item>
        </item>
   </menu>
</tm_user_device_menu>


<!-- stylesheet -->

<xsl:variable name="nService">
                                <xsl:value-of select="count
(tm_user_device_menu/menu/item/item_service)" />
                            </xsl:variable>

<xsl:for-each 
select="tm_user_device_menu/menu/item">                                 
       <xsl:variable name="iId">
<xsl:value-of select="./@item_id" />
</xsl:variable>
<xsl:variable name="sId">
<xsl:value-of select="./item_service/@item_service_svc_id" />
</xsl:variable>
<xsl:variable name="sNam">
<xsl:value-of select="./item_service/@item_service_usr_svc_nam" />
</xsl:variable>
<anchor><xsl:value-of 
select="./@item_title" />                                             
<xsl:choose>
<xsl:when test="$nService = 0">

<go href="/menu{$url.sessionId}?MNUITEMID={$iId}" />
</xsl:when>
<xsl:otherwise >
<go href="/service{$url.sessionId}?SID={$sId}&amp;USRSVCNAM={$sNam}" />
</xsl:otherwise>
</xsl:choose>
</anchor>
<br/>
</xsl:for-each> 

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