Advice on adding drop downs for products

[nerdgeek]

Hello all,

Have been searching around the FAQs and forum but because I don't know the exact name of what I want its a little hard !!

I will show you an example:

http://(sorry, site offline)/138/ind...products_id=26

At the bottom a user can select USB at extra charge.

In my chop I want the user to be able to customise a product by adding extra money onto the base amount.

Is this an extra module I've yet to find or is this something thats already in Zencart?

I'm using the latest version. Not sure what other info you need.

Thanks for helping or just looking at this post and not flaming me!