How can I write an ldap query to include all users from my active directory except those in a certain OU?

I'm having a debate with myself.  I'm just starting to understand LDAP Queries and wanted to pose a couple of questions because I can't seem to find the right information anywhere.

I get I can write an LDAP query that starts at the root of my Active Directory and return all the users in my AD environment.

Now..what if I want to traverse my directory and say give me all users in my Active Directory environment EXCEPT for the users in OU=Test,DC=somecity,DC=company,DC=com?

(&(objectCategory=user)(!(ou=test,dc=somecity,dc=company,dc=com)))

isn't working.  That returns all users regardless of their OU affiliation.  

Am I using the & operator incorrectly?  I also tried (what I thought was): give me all the users in the given OU...that didn't work either?

(&(objectCategory=user)(ou=test,dc=somecity,dc=company,dc=com)))

Any suggestions or assistance will be greatly apprciated!

V