Non so se ti servirà.... x IE 6.0
Uso i popup ma penso sia fattibile con degli iframes.

File : : test955.html
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 

<html> 
<head> 
<title>Untitled</title> 
<script language="JavaScript" type="text/javascript"> 
<!-- 
var loadedFile; 
var loadedRef; 
function loadFile(aFileName) { 
 loadedFile = aFileName; 
 loadedRef  = window.open('test955b.html',null,"height=0, width=0, menubar=no, toolbar=no,resizable=no,scrollbars=no" ); 
} // function loadFile(aFileName) 

function play() { 
 //------------ Pour savoir sur quelle page on se trouve 
 //             j'ai créé dans chaque page une fonction getPage 
 if (loadedRef.getPage() == 'a') { 
  loadedRef.a(); 
 } else { 
  loadedRef.b(); 
 } 
} 
//--> 
</script> 

</head> 
<body onunload="loadedRef.window.close()"> 

Clica su uno dei 2 pulsanti e poi clicca XXXX 
<input type="button" value="Carica file 1" onclick="loadFile('test955c.js')"> 
<input type="button" value="Carica file 2" onclick="loadFile('test955d.js')"> 
<input type="button" value="XXXX" onclick="play()"> 


</body> 
</html>
File : test255b.html
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 

<html> 
<head> 
<title>Untitled</title> 

</head> 
<body onload="window.resizeTo(0,0);window.moveBy(-1000, -1000);document.getElementById('script1').src=window.opener.loadedFile"> 
<script language="JavaScript" id="script1" type="text/javascript" ></script> 
</body> 
</html>
File : test955c.js
codice:
function a() { 
 alert('page a'); 
} 
function getPage() { 
 return 'a'; 
}

Fichier : test955d.js
codice:
function b() { 
 alert('page b'); 
} 
function getPage() { 
 return 'b'; 
}