I'm working on an RSVP form in an app, and I'm trying to figure out how to have two checkboxes mirror each other, when one is checked the other is not. Right now, my approach has been to have each checkbox bound to the `isComing` property, with one being checked on `!isComing`, but it's not working that way.

Here's what I tried:

HTML:

```
<script type='text/x-handlebars'>
<label>I&#39;m coming!</label>
{{view Ember.Checkbox checkedBinding="isComing"}}
<label>I can&#39;t make it.</label>
{{view Ember.Checkbox checkedBinding="!isComing"}}

{{#if isComing}}
<p>The rest of the form will be here.</p>
{{/if}}
</script>

```

JS:

```
window.App = Ember.Application.create();

App.ApplicationController = Ember.ObjectController.extend({
    isComing: false
});

```

This doesn't work. The first checkbox works fine, but the second checkbox is completely unaffected. Clearly, `!isComing` is not allowed...

This would be trivial to do in jQuery, and I thought about created a computed property that the second checkbox is bound to and that listens to `isComing`, but those don't seem like the **right** way.

Is there an easier way to do this with Handlebars or Ember? [Here's the fiddle if you want to experiment.](http://jsfiddle.net/mmerkes/3aZzn/)