I'm looking for an xml based scripting language

Hi all,
 
I'm looking for recommendations for an xml-based scripting language to add
to MyXaml.  I came across XEXPR
(http://www.w3.org/TR/2000/NOTE-xexpr-20001121/), but it looks a bit clumsy.
The idea here is to define in XML some basic workflows (no, not the complex
workflow server type stuff like BPEL), but rather the ability to call
functions (allowing variable number of arguments) that's hooked by the
parser into code-behind using reflection, and some basic expression
evaluation and loop control.  Some sort of syntax for getting/setting data
from the application's data store is necessary also.
 
Has anyone done anything like this or could point me in the right direction?
 
Thanks!
 
Marc