Any Alternate For OnBeforeUnload?

the bug of onbeforeunload is so obvious!

in IE 6 it will popup twice "sometimes"

I am using the following code

window.onbeforeunload = null;
window.onbeforeunload = confirmExit;
var executingPostBack = false;

function confirmExit()
{
if ( typeof executingPostBack != 'undefined' && !executingPostBack)
{
return 'Warning: Modified data has not been saved.' ;
}
}

In some cases, IE pops up it twice, for example, when we click a link
that contains "__doPostBack", onbeforeunload is fired the first time;
when the form is submitted, it is fired second time.

There is no way to work it around, because onbeforeunload is stupid, we
can't know whether the user clicks OK or Cancel.

I would like to use the following code with confirm so that I know
exactly what the user behaves

res = confirm("leaving?");
if (res==1)
{
alert("yes");
}
else
{
alert("no");
}

but I can't use this in onbeforeunload, because I can't stop it!
onbeforeunload always asks for something return, but if I return
anything, it will popup!