Query on Observe field

Take one example where there will be 2 combo boxes. One for the project and another one for types. I have used observe field for types combo box which observes project field and updates div of types. Now i need to observe types field using observe field(should consider both project and types values) and update a div without using any submit button.How can i do this. Please help me out.

re: Query on Observe field

If you want it to observe both fields, you may want to use observe_form instead of observe_field. Then you should be able to track all fields and make updates as necessary.