You have a grave misconception regarding how
JSP works. All that code that you have in the JSP is executing on the server long
before the page is sent to the browser. So it is impossible for it to react to on-page events such as dropdown selections.
Perhaps
this article will shed some light on what really goes on during the life-cycle of a JSP.
After reading it,
you should understand why the approach you propose can never work, and that you need to use Javascript, perhaps with the help of some Ajax, in order to accomplish what you are trying to do.
[ April 02, 2007: Message edited by: Bear Bibeault ]