How to determine if user selected a file for file upload?

If I have a

<input id="uploadFile" type="file" />

tag, and a submit button, how do I determine, in IE6 (and above) if a file has been selected by the user.

In FF, I just do:

var selected = document.getElementById("uploadBox").files.length > 0;

But that doesn't work in IE.

This works in IE (and FF, I believe):

if(document.getElementById("uploadBox").value != "") {
   // you have a file
}

this piece of code works in my local environment, hope it will also works in live

var nme = document.getElementById("uploadFile");
if(nme.value.length < 4) {
    alert('Must Select any of your photo for upload!');
    nme.focus();
    return false;
}