How to audit group membership changes?

How to audit group membership changes?

Hi guys
 
I'm having some problems auditing group membership changes. I have Win 2008 Active Directory. In my domain controller policy I have set up Audit Account Management to Succes/Failure but I can't get it to audit changes?
 
I have read the articles below:
 
Any Ideas what I am doing wrong?
 
Brgds
Liselotte

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