title: Regular expression to match anything except a few specific strings
body: <p>I am trying to figure out how to write a regular expression in my MVC model to make sure the user does not type "USA" or "United States of America" ignoring case.  Right now I have this:</p>
  
  <pre><code>[RegularExpression("^(?i)([U][S][A])|(^United States of America)$", 
   ErrorMessage = "county, not country")]
  </code></pre>
  
  <p>It does exactly the opposite of what I want.  You can only type "USA" or "United States of America".  How do I "not" that expression?</p>