Occurs when a single file from the list was uploaded to the server.
If the file is the only in the list or when all files in the list are uploaded - the onUploadComplete event fires.

Parameters:

realName- the real name of the file (as it's displayed in the control)
serverName - the file name that the server returns

myform.attachEvent("onUploadFile",function(realName,serverName){
    //any custom logic here
});