Check two elements are not deep equal

Is it possible in XML Schema 1.0 to ensure two elements are not deep
equal - the equivalent of this XPath:

//update[not(deep-equal(old/*, new/*))]

for this structure:

<update>
  <old>
    <data1>some value</data1>
    <data2>some other value</data2>
  </old>
  <new>
    <data1>some value</data1>
    <data2>some other value</data2>
  </new>
</update>

The <update> element should contain an <old> and a <new> with at least
one value different in the <new>... so in the example the test should
fail as the contents of both are the same.


thanks
andrew