A few Suggestions:
Read
this link on how to use the showModalDialog method.
Read
this link on how to create a JSP progress bar. The process described in this article is designed to work in a non-Struts JSP/Servlet environment, but with a little imagination you can make it work within the
Struts framework.
Change your submit button (<hmtl:submit>) to a regular button (<html:button>). When you call the showModalDialog method, the URL should be a Struts action that creates the TaskBean shown in the URL above and forwards to the progress Bar JSP. This starts whatever process you need to do in the background. The progress bar JSP resubmits itself every 5 seconds to check on the progress. When the taskBean is no longer running, use javaScript to cause the results JSP to be displayed in the main window and close the popup window. Because this is an asynchronous process, you will have to store the ActionForm for the results JSP in the session, rather than the request.
This is only one way to do it, but it should at least give you an idea of what can be done.