Was coding some new functionality and though I would post this, so that others can find it helpful.
Lets say you have a form that has a checkbox that will update the select dropdown box with different values, when the checkbox is clicked.
Something like the UI below.

Your html code might look like

On your server side you would provide a Action Method to filter out the data, something like

Now we got to add the javascript to listen to the checkbox event changed, something like this in jquery, since we are getting Json Result we will have to parse the json object to populate the dropdown box.

By doing so you will have something that shakes and updates the drop down box by some simple ajax calls 🙂