I think the example you want is covered in ...
Enterprise
Java Beans 3.0 pg 408 ..
Your probably off getting hold of a copy of the book but some quick notes ..
Their bean is annotated NOT_SUPPORTED for transactions , they inject an extended persistence context / entity manager, they do all their db work in a normal (NOT_SUPPORTED) method (as much as you like uncommitted) and then have another method like the one below ...
I don't want to post the listing as its from a book but ...
The entity(s) are committed to the database when the extended persistence context is enlisted in a transaction when the commitToDB method is called, the flush isn't needed as the context joins the transaction when the method is called.
"Eagles may soar but weasels don't get sucked into jet engines" SCJP 1.6, SCWCD 1.4, SCJD 1.5,SCBCD 5