Element Takes Enumerated List but has Attribute that Takes a String

All,

I'm trying to create the below structure

<Foo _Code="XYZ">ABC</Foo>

Where the element `Foo` takes a literal value from an enumerated list,
and the attribute `_Code` takes a (xs:)string. I have tried a few
different constructs based on research I've done. I can get the
enumerated list for the element but not the attribute or vice versa. 

Any suggestions would be appreciated. Here is what I've tried (doesn't
work).

	<xs:element name="Foo" type="FooType">
		<xs:complexType>
			 <xs:attribute name="_Code" type="xs:string"/>
		</xs:complexType>
	</xs:element>
	 <xs:simpleType name="FooType">
		<xs:restriction base="xs:token">
			<xs:enumeration value="ABC" />
			<xs:enumeration value="123" />
			<xs:enumeration value="DEF" />
		</xs:restriction>
	 </xs:simpleType>

Regards,
Adam