How do I get with X-Query the value of a tag ?

Hello !
I have a lot of XML trees in a Doctype.
I want to summate the value of the value tag.
This tag can be in every XML - Tree.
The value can be 1 to 20.
I use JDOM and Tamino 4.4.1
May somebody help me ?
Tree (example) :
<?xml version ......?>

-->                 <Bewertung HsFb="104"> 4</bewertung>

I tried : sum(/Publikation[Bewertung HsFb="(’)104(’)"])
…but it doesn’t work :O(



Thank you very much…everthing can be so easy ;O)

Does anybody know how I can realize that with JDOM ?
Here my code…but the x-query is wrong…I try different Styles, but ?

String pubquery2 = “sum(//Publikation[EinrichtungID=’”
+ einrichtungID
+ “’ and Jahr=’”
+ jahr