Monitoring Active Directory

Dear Friends
I am new to this forum.
I have a question about Active Directory.
I am working on make an application ldap compliant with Active Directory.

I am able to changes in the Active Directory when there is a change in the application database.

I am interest to the same thing in reverse order i.e. if any thing is changed in the active directory, I am recieve the event and make the relevant change in the application database.

If any when can help in this context, give some ideas how I can catch the events from active directory. I am using system.Directoryservices but I could not find an event services in the component.

A quick response will be highly appreciated.