OnClose event not detected by window

asked 2009-04-29 17:32:08 +0800

sumi
42 ● 1

I have a window A which opens another window B on click of a button .I use Executions.getCurrent.SendRedirect(url,null,null,"_blank") to browse to the new window.
This opens the Window B (It belongs to a different page) in a new browser window. This window starts a file transfer when the user clicks on START button.
What I want to do here is that I dont want the user to close the window abruptly, and want to disable the close button of the browser the user to click on the stop button provided.This would ensure that the file transfer is stopped before the user exits the window.
I have tried to set attribute closable="true" and onClose="event.stopPropogation()" .But this does not work as the window is still getting closed when the browser's close button is clicked.
Could someone please help me out?