Count element in orchestration

Hi All,

I'm developing the orchestration in BizTalk 2009, and would like count  the element.

For example, I would like to count the Address element numbers with the name start as "Tom"

<Root>
 <Header>
  <Name>Tom</Name>
  <Address>adress1</Address>
 </Header>
</Root>

In Xsl I can write the code like this:

count(/Root/Header[substring(Name,1,3)='Tom']/Address)

It is working fine, but if I paste the code to orchestration, it do not work.

Would like to know can I use the complex count in orchestration?

Thank you very much.