code: public boolean isModified(String propertyName)
      {
          gatekeeper.signIn();
          try
          {
              ChangeStack<String> stack = properties.get(propertyName);
              if (stack == null)
              {
                  return false;
              }
  
              return stack.isModified();
          }
          finally
          {
              gatekeeper.signOut();
          }
      }
docs: Determine whether or not the given property has been modified since it
  was last load or saved.
  
  @param propertyName
  the property to check
  @return <code>true</code> if this property has been modified since the
  last time it was loaded or saved; <code>false</code> otherwise