Hello,
May be you can use Confirm dialog box that JavaScript provides to know user response like "Ok" or "Cancel".
Please see this
link.
Of course if you still need to open a new browser window and then use some action to display "Ok, Cancel" buttons, you can do that using window.open() and passing the correct action URL as parameter. But unless specifically needed that would be too much for this kind of scenario.
Regards,
Amit