title: Rails: displaying a value dynamically calculated in my form
body: <p>In my new.html.erb, I have the following:</p>
  
  <pre><code>&lt;%= hidden_field :shipping_charges %&gt;
  &lt;%= label_tag :rush_shipment, "Rush My Shipment" %&gt;&gt;
  &lt;%= check_box_tag :rush_shipment, :checked =&gt; false, :onclick =&gt; "add_rush_shipment_charges()" %&gt;
  
      &lt;p&gt;My Shipping charges: &lt;span id="shipping_charges"&gt;&lt;/span&gt; 
  </code></pre>
  
  <p>In my javascript file, I have the following:</p>
  
  <pre><code>function add_rush_shipment_charges()
  {
      document.getElementById('shipping_charges').value = 25;
  }
  </code></pre>
  
  <p>When I click on the checkbox, I'm supposed to see 25 appear after Shipping charges, but nothing is happening. Any ideas.</p>
  
  <h1>EDIT:</h1>
  
  <p>Note that I edited the question to reflect the info I got from answer #1, but I am still not seeing anything.</p>