.I am using Ajax Uploader in my .net project, which is allowing user to upload multiple file at a same time.

While uploading new file/s, I want to display a pop up to a user if he/she is trying to upload a file which is already exist in database.(i.e. file with same name ).

If user says Yes then it should continue uploading file (Which will ultimatly overwrite in DB)
but if user says No then, how to cancel the upload for that specific file.

I want to achive this from client side.