I HAVE PROBLEM WITH MULTIPLE COMBOBOXES

[eluser]AlexPOWER[/eluser]
What are you mean Codeigniter?
I want to add product.
First i want to select in which category ,user can add product.

For exampel
first user select category, and than subcategory,and so on.
user must select, from 5 dropdown boxes(category and subcategory).

but i want to filterout results, i mean if user select option from first drop,which is main category, in second drop will show just options from selected category.