title: Knockout js. Is there a way to databind a textbox to both an observable and computed?
body: <p>Here's my jsfiddle:
  <a href="http://jsfiddle.net/bigtek/3rW9S/17/" rel="nofollow">http://jsfiddle.net/bigtek/3rW9S/17/</a></p>
  
  <p>My question is this:
  The "txtSum" textbox contains the sum of the two other textboxes.
  However, a user can enter a different number in the txtSum box.
  In this case, I want the "txtSum" box to be highlighted in red to tell the users that the numbers don't add up.</p>
  
  <p>Also, the allocate button will compute the two textboxes with their respective allocatpct.
  When this happens, I want to compute with whatever number is in the txtSum box, regardless of whether it is synched or not.</p>
  
  <pre><code>&lt;input type="text" data-bind="value:Sum" id="txtSum" /&gt;
  </code></pre>
  
  <p>(Am I doing this correctly?)</p>
  
  <p>Hope this makes sense..  thanks for you help.</p>