How to register a winlogon notification service like windows profsvc and gpsvc?

Question

I want to write a service to do some profile management before windows profsvc. I found this question Winlogon Notification Service before ntuser.dat is loaded but there is no anwser. I found that Citrix user profile management can register it as a service before profsvc.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Winlogon\Notifications\Configurations\Default

and the value is

SessionEnv, **Citrix UPM**,Profiles,Dot3svc,Wlansvc,GPClient,TermSrv,AUInstallAgent,*

What COM objects should I implement or what event notification should I register to write a service before profsvc? Is there any documents about this?

Thanks for your help in advance!