Duplicating orders

[anupam_sam]

On the confirm order page when the user click on the confirm order 'Button' the system sends the mail & show the message send to youremail@domain. and order confirmation message.

This is not instant & sometimes it takes more time than expected to send the confirmation mail and then it show the confirmation message.
Thus the user clicks on the confirm order button many times thinking nothing is happening but this used to place the same order multiple time i.e. Duplicating Orders (the no. of times the user pressed the confirm order button).

So how to disable the confirm order button once it is pressed?