ho provato così, di più non so

codice:
<HTML>
<HEAD>
<META NAME="GENERATOR" Content="Microsoft Visual Studio 6.0">
<TITLE></TITLE>
<SCRIPT LANGUAGE=javascript>
<!--
function miaFunzione(e)
{
	if (!e) var e = window.event;
	var target = (e.target)?e.target:e.srcElement;
	
	alert(indice(document.form1.ciccio));
	
	function indice(v)
	{
		var i;
		for(i = 0; i < v.length; i++)
		{
			if(v[i] == target)
			{
				return(i);
			}
		}
		return -1;
	}
	
	
}

//-->
</SCRIPT>

</HEAD>
<BODY>

<form id=form1 name=form1>
<INPUT type="text" id=text1 name=text1><INPUT type="text" id=text2 name=text2>


<INPUT type="text" name="ciccio" onclick="miaFunzione(event);" value="a">


<INPUT type="text" name="ciccio" onclick="miaFunzione(event);" value="b">


<INPUT type="text" name="ciccio" onclick="miaFunzione(event);" value="c">


</form>

</BODY>
</HTML>