XML Schema

In the XSD is it possible to specify, if the element value is "X" and the
following elements must start with ?

For Ex:

<Tasks>

<Task>

<Name>X</Name>

<Xlong>long text</Xlong>

<Xshort>short test</Xshort>

</Task>

<Task>

<Name>Y</Name>

<Ylong>long text</Ylong>

<Yshort>short test</Yshort>

</Task>

</Tasks>

Thanks and Regards,

Chandu