Validate Xml node with XPath

[tnf]

Aside of using XSD, is it possible to validate that all \[code\]<AAA>\[/code\] nodes contain \[code\]<BBB\[/code\]> with XPath?For example, I need to verify that count of //AAA/CCC = count of //AAAI need to do this in one expression, if it's possible\[code\]<root> <AAA> <CCC/> </AAA> <AAA> <BBB/> </AAA></root>\[/code\]