Abhishek, thank you for the informative tutorial. Can you confirm that these steps hold true for OpenERP 7.0 as well? Also is it possible to insert additional workflow steps into an existing module? Say for example if I wanted to add a step to the invoicing module, could I do this without hacking the original invoice module? Thanks again.

actually I did this workflow example in openerp v7 itself, So please go through that and if you have any doubts you can post it as a comment here. Thanks

As per my knowledge we can inherit an existing workflow, thereby you can add the required node which has some tasks