validation - writeback in forms


i have a form like this:

<% form_tag :action => "foo1"
   <%=select_tag ("user", "name", options_for_select(someArray))%>

   <%=select_tag ("formdata", "language1",
   <%=radio_button ("formdata", "language1_level, 3%>

<% end>

the controller has 2 functions, foo0 (displays the formular) and foo1
(validates data in params[:user])

if there is something wrong it renders the foo0 again, but only displays
the entered contend of params[:user].

HOW do i get to display the enterd data for params[:formdata]. All
formdata is not part of the model user, so i can't just change that.
Hopefully you understand. This text is somehow messy.



can anyone at least give me a hint. don't need the solution, just the
direction to it.