<script>
function getStatus(name){
var inps = document.getElementsByName(name);
//alert(inps);
//alert(inps.length);
var i = 0;
var checked;
for(i = 0; i < inps.length; i++){
//alert(inps[i].value);
//alert(inps[i].name);
if(inps[i].value == "main"){
var checked = inps[i].checked;
alert("got the value main");
}
//alert(inps[i].checked);
//alert(inps[i].type);
}
for(i = 0; i < inps.length; i++){
inps[i].checked = checked;
}
}
</script>
january <input type='checkbox' value = 'main' name = 'January' onblur='getStatus("January")' />
january item 1<input type='checkbox' value = '23' name = 'January' onblur='getStatus("January")' />
january item 2<input type='checkbox' value = '2' name = 'January' onblur='getStatus("January")' />
january item 3<input type='checkbox' value = '30' name = 'January' onblur='getStatus("January")' />
january item 4<input type='checkbox' value = '14' name = 'January' onblur='getStatus("January")' /><br /><br />
February <input type='checkbox' value = 'main' name = 'February' onblur='getStatus("February")' />
February item 1<input type='checkbox' value = '25' name = 'February' onblur='getStatus("February")' />
February item 2<input type='checkbox' value = '14' name = 'February' onblur='getStatus("February")' />
February item 3<input type='checkbox' value = '6' name = 'February' onblur='getStatus("February")' />
February item 4<input type='checkbox' value = '27' name = 'February' onblur='getStatus("February")' />
the event is actually onblur so you have to click on any of the first check boxes (january or february) and click anywhere on the body so trigger the onblur event.
actually you have to change that event later on...but that works...