attribute declaration

This is a very basic question and I am sorry to bother most of you, but if someone would straighten me out I would greatly appreciate it.

I am having trouble declaring an attribute in my schema.

the element and element's type look as follows:

<element name="Rules" type="rul:RulesType"/>

 <complexType name="RulesType">
  <sequence>
   <element name="Rule" type="rul:RuleType" maxOccurs="unbounded"/>
  </sequence>
  <!-- a variable name that will be returned at the termination of the rules engine -->
  <attribute name="Return" type="string" use="required"/>
 </complexType>

I am running Xerces 1.4.4 as a parser and it is giving me the following error:

[**] org.xml.sax.SAXParseException: Attribute "Return" is required and must be specified for element type "Rules".
at 4:24 of null - file:/C:/Program Files/Apache Tomcat 4.0/webapps/xmlp/xs/RulesInstance.xml

I appreciate the help!!

Joe