I don't think that you have the correct attibute. It is going to be part of the ADsPath. The attribute that you most likely want to use is the one that has the NT4 naming convention. (I do not recall what the attibute name is and I am not at work to look it up). Get youself a good LDAP browser (Softerra is what I use), and you can look at what all of the attibutes are.
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