calendardateselect + observe_form ?

=begin
I am using http://code.google.com/p/calendardateselect/ to make
date-selection easier.
This is my current code. I'd like the selection of a date to trigger the
observe_form and call the partial to be rendered.
My current attempt is to update a hidden field within the form when a
date is
selected, because plain date selection did not seem to work.
Did I just screw up the observe_form / form_remote_tag setup?
Is there a better option for date selection which will easily trigger
the observe_form?
=end

## controllers/dictated_exams_controller.rb
class DictatedExamsController < ApplicationController

  def index
    @users = User.all
    @from = Date.new
  end

  def filter_widget
    text = ""
    params.each { |a, b| text << "#{a} => #{b} <br />"}
    render :text => text

  end

end

## views/dictated_exams/index.html

<center>
<% form_remote_tag :html => {:id => 'input', :action =>
    url_for(:controller => "dictated_exams", :action => "filter_widget")
} do || %>
<%= collection_select :widget_user, :id, @users, :id, :name,
  { :prompt => true }
%>
<%= hidden_field 'date', '' %>
<%= calendar_date_select_tag "calendar", Date.today, :time => false,
    :valid_date_check => "date < (new Date()).stripTime()",
    :onchange => "date.value = $F(this)"
%>
<% end %>
</center>

<%= observe_form :input,
        # The field to observe
#:with => :id,
        # The input to validate
:on => "onselect",
#:frequency => 0,
        # The frequency in seconds to watch for changes
:url => {:action => 'filter_widget', :controller => 'dictated_exams' },
        # The action to call when changes occur
:update => :filter_counts
        # Name of the <div> to update
%>

<br/>
<div id="filter_counts">
<%= render :text => "Results will be listed here." %>
</div>