Sub Category under Main Category

[Guest yohan]

I have category and sub category like below:

- Main A

* sub Main A.1

* sub Main A.2

- Main B

* sub Main B.1

* sub Main B.2

I want to create that if i click on main category, the sub category will show. So, if i click on Main A, it will show:

- Main A

* sub Main A.1

* sub Main A.2

- Main B

and when i click on Main B, will show:

- Main A

- Main B

* sub Main B.1

* sub Main B.2

I have tried to modify the script, but i can't. I just can modify to make special event. For example, you can see at: http://heru.indoproduk.com/

For category and subcategory, i want to show like http://www.indoproduk.com. At this site, i use Zen Cart.

Anyone can help me?

Thanks