Also, check out http://h30507.www3.hp.com/t5/blogs/blogarticleprintpage/blog-id/TechnicalSupportServicesBlog/article-id/759 regarding the More Than One VTL Question. JorgeP's suggestion is also a great one to get you started (http://h30507.www3.hp.com/t5/blogs/blogarticleprintpage/blog-id/TechnicalSupportServicesBlog/article-id/740)
This one is also a good article, which contain links to other articles, http://h30507.www3.hp.com/t5/blogs/blogarticleprintpage/blog-id/TechnicalSupportServicesBlog/article-id/118