Uncheck 4 Of 5 Checkboxes Inside Same Array

I have a pretty simple survey form, with 5 checkbox answers, one of them being "None of the Above". All 5 are part of the same question1[] array. My goal is to have a function that unchecks the other 4 boxes when None of the Above is checked. The problem is that since None of the Above is part of the question1 array, it unchecks itself. So how do I separate this None of the Above option? After all, it is still a valid answer to question 1, so I don't want it to sit in a different array just because...

Here's what I have now:
Java:
function SetValues(Form, CheckBox, Value){
var objCheckBoxes = document.forms[Form].elements[CheckBox];
var countCheckBoxes = objCheckBoxes.length;
for(var i = 0; i < countCheckBoxes; i++)
objCheckBoxes[i].checked = Value;
}

HTML:
<input id="question1" name="question1[]" type="checkbox" value="Answer 1"> 1<br>
<input id="question1" name="question1[]" type="checkbox" value="Answer 2"> 2<br>
<input id="question1" name="question1[]" type="checkbox" value="Answer 3"> 3<br>
<input id="question1" name="question1[]" type="checkbox" value="Answer 4"> 4<br>
<input id="question1" name="question1[]" type="checkbox" value="None of the above" onclick="SetValues('form1', 'question1[]', false);"> None of the above <br>

So again the issue with this code is that since None of the Above is inside the question1 array, it unchecks itself as well.