// The client side event SplitterBarPositionChanging takes two parameters, sender and e.
// Sender is the object which is raising the event
// e is the SplitterBarPositionEventArgs
function WebSplitter1_SplitterBarPositionChanging(sender, e) {
var websplitter = $find("WebSplitter1");
// Get new size of previous pane
var newSizePrevPane = e.get_prevPaneNewSize();
// Get old size of previous pane
var oldSizePrevPane = e.get_prevPaneOldSize();
// Get new size of next pane
var newSizeNextPane = e.get_nextPaneNewSize();
// Get old size of next pane
var oldSizeNextPane = e.get_nextPaneOldSize();
if (!confirm("Do you want to change the previous pane size from"
+oldSizePrevPane+" to "+newSizePrevPane+"?"))
e.set_cancel(true);
}