logging into different logfiles depending on parameter

[Edwin]

Hello,
I'm trying to log in separate logfiles, depending on a parameter in my
application. Until now I'm unable to.
I have read about filters and what I tried is :

in my app :

log4net.GlobalContext.Properties["myparam"] = "xyz";

log.Info("message 1");

log4net.GlobalContext.Properties["myparam"] = "abc";

log.Info("message 2");


I'd like to have the 2 messages in different files. The filter I used is  :
      <filter type="log4net.Filter.PropertyFilter">
              <acceptOnMatch value="true" />
              <key value="myparam" />
               <stringToMatch value="xyz" />
      </filter>
      <filter type="log4net.Filter.LevelRangeFilter">
        <levelMin value="ALL" />
        <levelMax value="FATAL" />
      </filter>
      <filter type="log4net.Filter.DenyAllFilter" />



The result is that all messages are logged in all logfiles.
How should/can I solve this ?

Thanks,
Edwin