I need to understand how I can validate the xsd:element choosen in an xsd:choice
to another element in the schema. Below is part of my schema.

<?xml version="1.0" encoding="UTF-8" ?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<xsd:simpleType name="stCommand">
<xsd:restriction base="xsd:string">
<xsd:enumeration value="Choce1" />
<xsd:enumeration value="Choice2" />
<xsd:element name="Document1">
<xsd:element name="Command" type="stCommand"/>
<xsd:element name="Data1" type="xsd:string"/>
<xsd:element name="Data2" type="xsd:date"/>

What I would like to see happen, is as follows. When Command = Choice1,
then the choice must be Data1. When Command = Choice2, then the choice must
be Data2.

How can I enforce this constraint using XML Schemas?