How to hide modalpop automatically after some seconds

I'm using this code behind but doesn't seem to work..

ProgressBarModalPopupExtender.show();

 System.Threading.Thread.Sleep(2000);

        ProgressBarModalPopupExtender.Hide();


please suggest me any way to get rid of this..

You would need to use a timer, either in your parent application or on the modal form.
From parent, when time limit is expired, call modalpopup.Close() from your time event.
From the modal form, disable the timer and call Close() from your time event.