Deployment plan to override values in web.xml and ejb-jar.xml

All,
Could someone tell me if it is possible to use plan.xml to override <env-entry> values in web.xml and ejb-jar.xml.

I have an entry like,. in web.xml and ejb-jar.xml(one entry for each of my EJBs). In my application, I lookup the value using JNDI like, ic.lookup("java:comp/env/my_env"). If I have hardcoded values in web.xml and ejb-jar.xml, everything works fine. Now I need to use deployment plan to override the value to staging and production. My plan.xml looks like this

<?xml version='1.0' encoding='UTF-8'?>
<deployment-plan xmlns="http://xmlns.oracle.com/weblogic/deployment-plan" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.oracle.com/weblogic/deployment-plan http://xmlns.oracle.com/weblogic/deployment-plan/1.0/deployment-plan.xsd" global-variables="false">
  <application-name>myapplication.ear</application-name>
  <variable-definition>
 
    <variable>
      <name>SessionDescriptor_invalidationIntervalSecs_12677202001481</name>
      <value>60</value>
    </variable>
    <variable>
      <name>my_env</name>
      <value>"stag"</value>
    </variable>
  </variable-definition>
  <module-override>
    <module-name>myapplication.ear</module-name>
    <module-type>ear</module-type>
    <module-descriptor external="false">
      <root-element>weblogic-application</root-element>
      <uri>META-INF/weblogic-application.xml</uri>
    </module-descriptor>
    <module-descriptor external="false">
      <root-element>application</root-element>
      <uri>META-INF/application.xml</uri>
    </module-descriptor>
    <module-descriptor external="true">
      <root-element>wldf-resource</root-element>
      <uri>META-INF/weblogic-diagnostics.xml</uri>
    </module-descriptor>
  </module-override>
  <module-override>
    <module-name>myapplication.war</module-name>
    <module-type>war</module-type>
    <module-descriptor external="false">
      <root-element>weblogic-web-app</root-element>
      <uri>WEB-INF/weblogic.xml</uri>
      <variable-assignment>
        <name>SessionDescriptor_invalidationIntervalSecs_12677202001481</name>
        <xpath>/weblogic-web-app/session-descriptor/invalidation-interval-secs</xpath>
      </variable-assignment>
    </module-descriptor>
    <module-descriptor external="false">
      <root-element>web-app</root-element>
      <uri>WEB-INF/web.xml</uri>
      <variable-assignment>
        <name>my_env</name>
        <xpath>/web-app/env-entry/env-entry-value</xpath>
        <operation>replace</operation>
      </variable-assignment>
    </module-descriptor>
  </module-override>
  <module-override>
    <module-name>myapplication.jar</module-name>
    <module-type>ejb</module-type>
    <module-descriptor external="false">
      <root-element>weblogic-ejb-jar</root-element>
      <uri>META-INF/weblogic-ejb-jar.xml</uri>
    </module-descriptor>
    <module-descriptor external="false">
      <root-element>ejb-jar</root-element>
      <uri>META-INF/ejb-jar.xml</uri>
      <variable-assignment>
        <name>my_env</name>
        <xpath>/ejb-jar/enterprise-beans/message-driven/[ejb-name="TableStarMessage"]/env-entry/[env-entry-name="my_env"]/env-entry-value</xpath>
        <operation>replace</operation>
      </variable-assignment>
    </module-descriptor>
  </module-override>
  <config-root>C:\oracle\Middleware\user_projects\domains\base_domain\servers\AdminServer\upload\myapplication.ear\app\plan</config-root>
</deployment-plan>

Relevant portion of my ejb-jar.xml is

I have been looking on the web for solution, the closest one I found was http://forums.oracle.com/forums/thread.jspa?threadID=971474&tstart=223

But still I am not able to get through this. Please let me know what I miss here.
Thanks

Posting the answer just in case, someone will need in future

<xpath>/web-app/env-entry/env-entry-value</xpath> - this was wrong.

the correct expression is <xpath>/web-app/env-entry/[env-entry-name="bm_env"]/env-entry-value</xpath>

Thanks
Kalai