Try setting your constant sum to use this custom JavaScript verification:
var notApplicableQuestion = $('#[% QuestionName() %]_div').nextAll('.select').attr('id').replace(/_div$/, '');
var notApplicable = false;
$('input[name="hid_list_' + notApplicableQuestion + '"]').val().split(',').forEach(function(item){
if (SSI_GetValue(notApplicableQuestion + '_' + item)) {
notApplicable = true;
}
});
if (!notApplicable) {
$('input[name="hid_list_[% QuestionName() %]"]').val().split(',').forEach(function(item){
if (!SSI_GetValue('[% QuestionName() %]_' + item)) {
strErrorMessage = 'my error message...';
}
});
}