Look-ahead during XML Schema parsing

Hi all

I writing a custem SAX parser for which I want to use Xerces 2 to 
provide me with XML Schema validation. This I've been able to do using 
XMLSchemaValidator. However, I also want to use the XML Schema to 
control the parsing. To do this I want to look ahead from the current 
element and see what elements/attributes are allowed as children or 
siblings. I have yet not found a way to do this, but I have a feeling 
I'm missing something obvious. Is this possible and what would be the 
best way of doing it?
/niklas