Logging Windows authentication

I have an ASP.NET application which uses Windows authentication. A certain Windows group has been given access:

<authentication mode="Windows" />
    <authorization>
      <allow roles=".\MyAppUsers" />
      <deny users="*" />
    </authorization>
 
Now I want to log in a database table which users succesfully and unsuccesfully try to access the application. But I don't want this for every request a user is making; this would result in an overload of authentication logging. Is there functionality in the ASP.NET Framework to determine if a user succesfully logs in?
Thanks,
Nils Gruson

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