Dropdown adding to list (text field)

Hello

Right.

I'm designing a literature request page.

There are 4 catergories of literature. Each with seperate items in each.

I want users to be able to request quanities of item/s ergo. 1 Red Pack, 9 Green Packs in one request

I need this to take up as little space as possible on the page and have concluded a method, currenty, out of my skills.

I figure 4 radio buttons indicating the 4 catergories. Each button changes the content of a single dropdown menu coupled
with a text box for inputing the quantity required. Once quantity and item has been slected, I want an "Add" button to combine the
quantity and item picked and place it into a Text field? were the list will be stored and added to until the request is complete.

Can anyone help my fumberling brain.

Thankyou for you anticipated help peeps.

If this is a web page, then you can store all the selected data into local JavaScript variable and then send it to the server for processing (ASP, JSP, PHP, etc.).