Anthony,
Uploader provide JavaScript API to let you listen the event.
OnSelect - to know files have been added into queue.
OnQueueUI - to get the files information.
OnProgress - to get the progress information.
OnPostback - to know the file is uploaded, and prepair to fire the server event. you can return false to cancel it, and do the postback later.
And you may use the
ManualStartUpload property to control when it should start file transfering.
You need use all these things and write a lot of JavaScript code to implement your request.
Regards,
Terry