Using environment variables in the config

Hi
I am new to log4net (have used log4j etc). I wanted to set my config
using environment variables, and have been having mixed success.
 
  <!-- file is set to be a FileAppender -->
  <appender name="file" type="log4net.Appender.FileAppender">
    <file value="${JCE_LOG_FILE}"/>
    <appendToFile value="false"/>
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date{ISO8601} [%thread] %-5level
%logger - %message%newline" />
    </layout>
  </appender>

This works fine (the log file is set up to be a combination of appname,
user, date etc)
 
  <!-- Set root logger -->
  <root>
    <level value="${JCE_LOG_LEVEL}" />
    <!--level value="INFO" /-->
    <appender-ref ref="console" />
    <appender-ref ref="file" />
 
  </root>

This doesn't - ie env var substitution does NOT seem to be used on the
'level' tag?
 
Alasdair
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