How can I express it in HQL

I already found this request. SQL returns the result that I want, but I cannot figure out how to express a query in HQL.

Here's the SQL :

select      thread.ThreadId,
            thread.Title,
            thread.CreatedOn, 
            thread.ViewCount,
            thread.CreatedBy,
            thread.ForumId 

from Threads thread 
where 
    (thread.ThreadId in(select post.ThreadId from Posts post 
    where (post.CreatedBy=2 )))

AND

(2!=(select TOP 1 post2.CreatedBy from Posts post2 
        where (post2.ThreadId=thread.ThreadId ) ORDER BY post2.CreatedOn DESC))

I think I need to use DetachedCriteria to create a correlated subquery, but I'm having real problems.

Here where I am :

DetachedCriteria latestPostInThread = DetachedCriteria.For(typeof (ForumPost), 
                    "post2")
            .Add(Expression.EqProperty("post2.ThreadId", "post.ThreadId"))
            .AddOrder(Order.Desc("CreatedOn"))
            .SetFirstResult(0)
            .SetMaxResults(1);

and for the main request :

ICriteria critMain = CreateCriteria(typeof (ForumPost), "post")
            .Add(Expression.Eq("CreatedBy",user.ID))
            .Add(Subqueries.Ne("CreatedBy", latestPostInThread));

This is clearly wrong - I need to get userId from lastPostInThread in order to use it as my subquery, but I'm completely incapable.

Any help would be greatly appreciated! I hate going back to SQL for something that I'm sure of nHibernate is not so difficult to achieve.