trouble in passing select tag values in a rails application

new on rails, i am having problem in passing select_tag value(in the view file) to controller.

my view controller file is like

class ProjectStatusController < ApplicationController

  def index     @projects = Project.find(:all, :select => "name")   end

  def show     lookup = params[:project]     @rows = Project.find_by_lookup(lookup)   end end and view file is like

<% form_tag("project_status", :controller => "ProjectStatus", :action => "show", :method=>'get' ) do %> <%= select_tag 'project', options_from_collection_for_select(@projects,"id", "name"),:onchange => "this.form.submit();" %> <% end %> <% if !@rows.nil? @rows.each do |row| end %> <%= row[:name] %> <% end %>

what i basically want to achieve is this - based on the selected value from select tag i want to display information(on the same view page) of selected item from the database