variables in XSD?

Hello.  Is there any way to use variables w/in XSD?

I would like to bind the maxOccurs attribute of an element to a value
defined elsewhere in the XSD file.  It could either be defined as its
own variable or as a computed value.  I've been working in XSL for so
long, I just sort of assumed I could do this:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">

  <xs:element name="root">
    <xs:complexContent>
      <xs:sequence>
        <xs:element name="foo" minOccurs="0" maxOccurs="$n"/>
      </xs:sequence>
    </xs:complexContent>
  </xs:element>

  <!-- I know this is wrong -->
  <xs:variable name="n">23</xs:variable>

</xs:schema>

Obviously, this won't work.  But is there any way it could work?  I
don't think so, I just thought I'd double-check.

Thanks.