OverWrite Prompt

Has Anyone figured out yet how to prompt for an overwrite if file names match when uploading files? I have been able to get the logic to work, as you can see i created a fake var just to trigger a confirm ( if (x == 1) ). 

I can't seem to figure out what to replace( if (x == 1) ) to ( if (existing file name = the uploading file name).

function Upload() {
        var x = 1;
        if (x == 1) {
            var y = confirm("OverWrite File");
                if (y == true) {
                document.forms.formBuffer.submit();
                } else {
                alert("Upload Aborted");
                close();   
                }
        } else {
            document.forms.formBuffer.submit();
        }
    }

I am now able to get the uploading document name, and parse the extention that will be in the file(uploading inputbox) to look like test.txt instead of the full path ( example C:\documents\someFolder\test.txt ) and if i hard code a name to compare it with i see results. 

But now i need to try to get the server side file name to compare with my uploading document name. Anyone know i can get this name? I trying to figure different ways in using php, VBscript or asp and then somehow try to call a function or variable in javascript or call javascript in The VBscript stuff.

Any help would be most appreciated.


(heres what i got so far) 
function Upload() {

        var x = document.getElementById("file").value.replace(/^.*[\\\/]/, '');  // parse file to only show test.txt
        if (x == ("test.txt")) {
            var y = confirm("OverWrite File ?");
            if (y == true) {
                document.forms.formBuffer.submit();
            } else {
                alert("Upload Aborted");
                close();
            }
        } else {
        document.forms.formBuffer.submit();
        close();
        }
    }     

ya scratch all that, it seems i was modifying the wrong file. I have to modify the Public Function Upload() in wexGeneric.asp file. This way i can verfiy if file exists by "If FSO.FileExists(FSO.BuildPath(path, uploadedFileName))"

seems than i can add "Response.Write("<script>javascript: confirmation();</script>")", to call a js function where i call a confirm box "if (confirm("OverWrite File?") == true)", but now i need to find a way to send back to server side. 

I need to either try to implement ajax or something to either re-submit the form or cancel the upload process and close the stream.....Stuck on this part now