Is it possible to attach composition line to an enumeration?

Hi,

I'm using ArgoUML to model an XML schema, and I was wondering if it's 
possible to connect a composition line to an enumeration box as shown in 
the diagram under "Modeling Simple Types" in:

http://www.xml.com/pub/a/2002/08/07/wxs_uml.html

I've tried to do it by dragging the composition line from the class to the 
enumeration box, but the composition line never appears on the diagram.

Thanks very much,
Andy Halper