How do I return the number of RTC Work Item children with an attribute value to Focal Point?

I have an integration between Focal Point and Rational Team Concert (RTC).  I can successfully create an Integration link, but I need an attribute to return the number of RTC Work Item children matching a given attribute (Flags attribute is set to Blocked).

I am open to suggestions, but thought it would be easier to run a Focal Point XPathValueFetcher to the RTC linked form to search its children.

I referenced the XPathValueFetcher business rule on IBM site

http://publib.boulder.ibm.com/infocenter/rfphelp/v6r5/index.jsp?topic=%2Fcom.ibm.rational.fp.help.doc%2Ftopics%2Fc_xpathvalue_businessrule.html  and other notes to create the following expression

=XPathValueFetcher('RTC Integration Link Attribute',"/rtc_cm:com.ibm.team.workitem.linktype.parentworkitem.children/?oslc_cm.properties=rtc_cm%3Aflags%7B*%7D","//rtc_cm:flags/dc:children[text()]","Flags","run_at=1")

It returns the linked RTC work item and its summary, but not the number of children with the Flag attribute. 

The Focal Point attribute is type:  text

Any thoughts?  Should I do some kind of summary in RTC and set it to an RTC attribute first?  (If so, I need help on that approach as well.)