gmaravel,
You can do this if you modify the templates used for generation. More instructions on how to modify the templates can be found in the Hibernate Quickstart, section 5.5.
You can get to the hibernate guide from withing MyEclipse here: Help > Help Contents > MyEclipse Learning Center > Spring/Hibernate Development > Getting Started > Hibernate Development.
You will most likely need to modify the persistentclass.hbm.vm file.
Hope this helps,
Brian.