Fired when the column moving is finished (the column is dropped at the target position) but before the column is actually moved. You have a chance to cancel the moving here.
DayPilot.Kanban.onColumnMove(args);
The source data object is accessible as args.column.data.
<div id="dp"></div>
<script type="text/javascript">
var dp = new DayPilot.Kanban("dp");
// ...
dp.columnMoveHandling = "Update";
dp.onColumnMove = function(args) {
if (!confirm("Do you really want to move this column?")) {
args.preventDefault();
}
};
dp.init();
</script>