<input type="checkbox" class="whatever" name="whatever" value="1">
<input type="hidden" class="myHidden" name="hiddenField" value="">

<script>
// whether checked or unchecked, this will run
$('.whatever').check(function() {
    var value = $(this).val();
    $('.myHidden').val(value);
});

if ( $('.myHidden').val() == '1' )
    $('.whatever').checked();
</script>