You cannot do this with just JSP. Please read
this article on how JSP works.
JSP can help you created the initial HTML sent to the browser, but once the page is loaded you'll need to use JavaScript to make changes to the page.
So if, for example, the user choices a count, you'd create that many elements and place them in the correct location within the DOM.
I'd advise using jQuery (a popular JavaScript library) to make the whole thing much easier.