Set an Active Directory ExtendedRight

Hi Everyone I would like to set the DS-Install-Replica (Add/Remove Replica In Domain) on the domain using Powershell.

http://msdn.microsoft.com/en-us/library/ms684351%28VS.85%29.aspx

This is the script

$objLDAP = [ADSI]"LDAP://DC=Devenvx,DC=infra,dc=ss,dc=gov,dc=au"
    $objSecurity = $objLDAP.psbase.ObjectSecurity

    ## set the rights and control type
    $objControlType = [System.Security.AccessControl.AccessControlType]::Allow
    $objRights = "ExtendedRight"
    $strGUID = "9923a32a-3607-11d2-b9be-0000f87a36b2"
    #$objInherit = [System.DirecotryServices.ActiveDirectorySecurityInheritance]::All
    $objInherit = [System.DirectoryServices.ActiveDirectorySecurityInheritance]"All"
   
    ## who does this apply to
    $objwho = New-Object -TypeName System.Security.Principal.NTAccount -ArgumentList "", "AA-L-AdditionalDC"

    # apply
    $ObjnewACE= New-Object -TypeName System.DirectoryServices.ActiveDirectoryAccessRule -ArgumentList $objwho, $objRights, $objControlType, $objInherit, $strGUID
    $objSecurity.AddAccessRule($ObjnewACE)
    $objLDAP.psbase.CommitChanges()

Works fine, except when I go into ADSIEdit, the permission hasn't been set, instead it just seems to add the group and sets nothing.

Any ideas?