Register userid when useing the EventLog

[TobyOne]

I use the eventlog to track user envoked events in a asp.net/vb.net application I have. The system uses impersonation and I kind of did hope that the user id would show up in the eventlog when I use the WriteEvent method. But it doesn't. The user column in the eventlog just says 'N/A'.

How do I set the userid, if it is at all possible?

Regards,
Toby