Validate loops in XML using XSD

Hi,

In my application i have a parent node which contains many child nodes. I want to validate the number of child nodes using another XML node elements just before the child nodes.

In the example below, i want child nodes of 'CONTENTS' node should not be more than 5.

How i can do this XML validation using XSD validation?

<DATA><COUNTER>5</COUNTER><CONTENTS><CONTENT ID="1" ></CONTENT><CONTENT ID="2" ></CONTENT><CONTENT ID="3" ></CONTENT><CONTENT ID="4" ></CONTENT><CONTENT ID="5" ></CONTENT><CONTENT ID="6" ></CONTENT></CONTENTS></DATA>

Thanks,

IamHuM