Disculpa es que no habia refrescado mi pantalla y no lei esa parte ya modifique a lo siguiente
<script language="javascript">
function update(id)
{
id = liquida.document.getElementById(id);
cant = liquida.document.getElementById(id).value;
valor = "valor"+id;
total = "total"+id;
valore = liquida.document.getElemenById(valor).value;
totale = 0;
totale.value = cant.value * valore.value;
liquida.document.getElementById(total).value = totale;
}
</script>
<form name="liquida" method="post" action="">
<table width="80%" border="0" cellspacing="0" cellpadding="0">
<tr>
<td>Nombre</td>
<td>Cant</td>
<td>Valor</td>
<td>Total</td>
</tr>
<tr>
<td>Perico</td>
<td><label><input name="A1" type="text" id="A1" size="8" maxlength="8" onchange="update(this.id)"></label></td>
<td><label><input name="valorA1" type="text" id="valorA1" size="8" maxlength="8" onchange="update(this.id)"></label></td>
<td><label><input name="totalA1" type="text" id="totalA1" size="8" maxlength="8" readonly></label></td>
</tr>
<tr>
<td>Juan</td>
<td><label><input name="A2" type="text" id="A2" size="8" maxlength="8" onchange="update(this.id)"></label></td>
<td><label><input name="valorA2" type="text" id="valorA2" size="8" maxlength="8" onchange="update(this.id)"></label></td>
<td><label><input name="totalA2" type="text" id="totalA2" size="8" maxlength="8" readonly></label></td>
</tr>
<tr>
<td>Pedro</td>
<td><label><input name="A3" type="text" id="A3" size="8" maxlength="8" onchange="update(this.id)"></label></td>
<td><label><input name="valorA3" type="text" id="valorA3" size="8" maxlength="8" onchange="update(this.id)"></label></td>
<td><label><input name="totalA3" type="text" id="totalA3" size="8" maxlength="8" readonly></label></td>
</tr>
<tr>
<td>Carlos</td>
<td><label><input name="A4" type="text" id="A4" size="8" maxlength="8" onchange="update(this.id)"></label></td>
<td><label><input name="valorA4" type="text" id="valorA4" size="8" maxlength="8" onchange="update(this.id)"></label></td>
<td><label><input name="totalA4" type="text" id="totalA4" size="8" maxlength="8" readonly></label></td>
</tr>
</table>
</form>