Checkboxes and checkboxes

I have multiple checkboxes that I need to make mutually exclusive; I am using this code and it works:

$("input[name=ckbprf]").click(function () { $(this).closest("table").find("input").not(this).removeAttr("checked"); });

Now the problem I'd like to solve: I need that if one of the checkboxes is already CHECKED, it remained CHECKED when I click on it.

It may be unchecked just only when I click on an other one.

Thank you.