How to extract essbase user in drillthrough definition

Hi, I'm building a webservice that makes use of the essbase drillthrough definition feature.  I was hoping to capture the Essbase user making the drillthrough request so I could log the user in my webservice.  We don't use SSO so the SSO_USERNAME token is not an option.  Appreciate if anyone has any ideas.  Otherwise, the $ATTR(ds,pos,gen,level.edge)$ expands to all the values needed to create the report.

<?xml version="1.0" encoding="UTF-8"?>

<foldercontents path="/">

  <resource name="Assets Drill through GL" description="" type="application/x-hyperion-applicationbuilder-report">

  <name xml:lang="fr">Rapport de ventes</name>

  <name xml:lang="es">Informe de ventas</name>