Since you have a countable number of options you can use an enumeration to restrict them. Replace your xs:element
declaration with this:
<xs:element name="Name" maxOccurs="unbounded" minOccurs="1">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="ABC"/>
<xs:enumeration value="CBS"/>
</xs:restriction>
</xs:simpleType>
</xs:element>