Prova questo
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled</title>
<script language="JavaScript" type="text/javascript">
<!--
function pippo(unaRiga) {
indiceRiga = unaRiga.rowIndex;
precedente = indiceRiga - 1 >= 0 ? indiceRiga - 1 : null;
successiva = indiceRiga + 1 < unaRiga.parentNode.rows.length ? indiceRiga + 1 : null;
alert('Riga : ' + indiceRiga + ' -> Prec : '+precedente + ' - Succ : '+successiva);
}
//-->
</script>
</head>
<body>
clicca su una riga:
<table summary="" border="1">
<tr onclick="pippo(this)">
<td>riga 1</td>
</tr>
<tr onclick="pippo(this)">
<td>riga 2</td>
</tr>
<tr onclick="pippo(this)">
<td>riga 3</td>
</tr>
<tr onclick="pippo(this)">
<td>riga 4</td>
</tr>
<tr onclick="pippo(this)">
<td>riga 5</td>
</tr>
</table>
</body>
</html>