SO fiddle

Test Fiddle mainly for SO Questions

by Nick Craver

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/overcast/jquery-ui.css">
<table>
  <tbody>
    <tr><th>Player</th><th>Score</th></tr>
    <tr><td>Jack</td><td>7</td></tr>
    <tr><td class="parent">Green Team</td><td></td></tr>
    <tr><td class="child">Mark</td><td>11</td></tr>
    <tr><td class="child">Tom</td><td>5</td></tr>
    <tr><td>Steven</td><td>8</td></tr>
    <tr><td>Greg</td><td>4</td></tr>
    <tr><td class="parent">Blue Team</td><td></td></tr>
    <tr><td class="child">Joe</td><td>10</td></tr>
    <tr><td class="child">Jill</td><td>12</td></tr>
    <tr><td class="child">Rachel</td><td>9</td></tr>
  </tbody>
</table>

CSS

.parent { font-weight: bold }
.child { color: #666; }

JavaScript

$("tr:has(td.parent)").each(function() {
    var sum = 0;
    $(this).nextUntil(':not(:has(td.child))').children(':nth-child(2)').each(function() {
        sum += parseInt(this.innerHTML, 10);
    });
    $(this).children(':eq(1)').text(sum);
});