Check Box - just checked value

Hi Folks

I have a check box with 10 options. How do I tell which option user just modified?

If user checks one item, how can I programatically know which one was checked (modified). I want to be able to uncheck an other option that must be unchecked if this value is checked.

e.g.: if user checks [5] then I want to uncheck [4] [6] and [7] and if user checks [6] then I must uncheck [4] [5] and [7].

there no place to set them to false before the click. ( only init and click methods )
I could store all the values and match them, but seems unnecessary.

Thanks