question about regex and schema

Hello list users,

I have the following complexType:

     <xs:complexType name="speccharType">
         <xs:choice minOccurs="0" maxOccurs="unbounded">
             <xs:element name="greek">
                 <xs:simpleType>
                     <xs:restriction base="xs:string">
                         <xs:enumeration value="\p{Greek}"/>
                     </xs:restriction>
                 </xs:simpleType>
             </xs:element>
         </xs:choice>
     </xs:complexType>

The aim should be to allow only greek characters inside an element  
with the speccharType. But when I am going to test it inside an  
instance document I only have the possibility to use the value  
"\p{Greek}" instead of greek characters. I think the regex is not  
suitable for my purpose. Unfortunately I am not very familiar with  
regex at the moment.

I hope my question is clear to the list users :-)

Thanks so much,
Andreas