How can i diasble serverside webexplorerbar event to fire using javascript

ClientSide itemClick event?

i have a clientSide and server side ItemClick event in WebExplorerBar,

if i do click on any item then my client side side script execute and

ask for confirmation

like confirm("Do yo want to process"), if user cliked on cancel, then

server side event should not be execute.

So how can i prevent to execute server side event?