title: Binding selected radiobox to enabling checkbox in Cocoa
body: <p>I haven't worked with Cocoa bindings a lot before, so I would need a little help here.</p>
  
  <p>I have a radio button group ( NSMatrix ) with three buttons and one checkbox.
  I want the checkbox to be enabled only when the last radio button is selected.</p>
  
  <p>Found a tutorial online which advised to bind the selected tag property of the radio button group to the enabled property of the checkbox. The last radiobutton needs to have a tag of 1, the others would need to have a tag of 0.
  This works great. </p>
  
  <p>The problem is, that if the checkbox is checked and the radiobutton selection is changed, it stays checked although it isn't enabled. I would want that the box gets unchecked when it changes to the disabled state.</p>
  
  <p>Any advise would be appreciated!
  Thanks in advance!</p>
  
  <p>Any way to achieve this without any code?</p>