The scripts you're looking for:
<span class="gridtotal"></span>
<script>
$(document).ready(updateGridTotal);
$(document).on('keyup', '#[% QuestionName() %]_div .numeric_input', updateGridTotal);
function updateGridTotal() {
var total = 0;
$('#[% QuestionName() %]_div .numeric_input').each(function(){
total += SSI_GetValue(this.id);
});
$('.gridtotal').text(total);
}
</script>
var total = 0;
$('#[% QuestionName() %]_div .numeric_input').each(function(){
total += SSI_GetValue(this.id);
});
if (total != 100) {
strErrorMessage = 'Error';
}