Hibernate version:3.1.3

Hi!
I have a problem using Hibernate with Websphere. I'd like to initialize Hibernate as a custom service.
My problem: if I use container connection pool for datasource (datasource in jndi), I need a resource reference, because I cannot set isolation level and authentication, but I don't know is there any way to set a resource reference to a Custom Service.

Anyway, has anybody initialized Hibernate under Websphere as custom service? I'd be very happy if somebody could give me a working example or step-by-step tutorial....

thx, Peter