Get File size in bytes using javascript works in IE

I want file size in bytes using javascript which works in IE i had already tried this

function getSize()
{
var myFSO = new ActiveXObject("Scripting.FileSystemObject");
var filepath = document.upload.file.value;
var thefile = myFSO.getFile(filepath);
var size = thefile.size;
alert(size + " bytes");
}

But it is not working in my asp.net website.

I am getting exception of "ActiveXobject"

Subramanyam