Hibernate 2.1.2

class A
{
B myInstanceOfB;
string label;
}

class B
{
string name;
}

List cats = sess.createCriteria(A.class)
.add( Expression.like("label", "F%")
.addOrder( Order.asc("myInstanceOfB.name") )
.list();

When i execute the query, I get an exception -> Could not resolve property: myInstanceOfB.name of:A

What's wrong ?
Thank you.
Richard.