If you're looking for help specifically with Struts, you should go to the Struts forum...
But this question really deals more with design of application flow rather than Struts directly - there are several choices you could make, depending on your application -
Restucture your application so that what is currently one form is spread across 3 real forms, save data in session on the server until all forms are filled in.
Write once, run anywhere, because there's nowhere to hide! - /. A.C.