Funziona benissimo. Ho preso i 4 primi campi

codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
<script language="JavaScript" type="text/javascript">
<!--
function guestForm(){
	var tot_isr = document.getElementById("tot_isr");
	var tot_vig = document.getElementById("tot_vig");
	var tot_bra = document.getElementById("tot_bra");
	var tot_gre = document.getElementById("tot_gre");
	
	tot_isr = parseInt(tot_isr.value, 10);
	tot_vig = parseInt(tot_vig.value, 10);
	tot_bra = parseInt(tot_bra.value, 10);
	tot_gre = parseInt(tot_gre.value, 10);
	
	var arrVal = new Array();
	arrVal[arrVal.length] = tot_isr ; 
	arrVal[arrVal.length] = tot_vig ; 
	arrVal[arrVal.length] = tot_bra ; 
	arrVal[arrVal.length] = tot_gre ; 

	ok = true;
	for (i=0;i<arrVal.length;i++) {
		for (j=0;j<arrVal.length;j++) {
	  		if (arrVal[i] != arrVal[j]) {
		 		ok = false;
			} // if (arrVal[i] != arrVal[j])
		} // for (j=0;j<arrVal.length;j++) 
	} // for (i=0;i<arrVal.length;i++) 
	alert(ok);

}
//-->
</script>

</head>
<body>
<input type="text" id="tot_isr">

<input type="text" id="tot_vig">

<input type="text" id="tot_bra">

<input type="text" id="tot_gre">

<input type="button" onclick="guestForm()">
</body>
</html>