fires the moment you drop the column to its target position
| sourceId | string | the source column id |
| targetId | string | the target column id |
| event | Event object | the native event object |
$$("datatable1").attachEvent("onBeforeColumnDrop",
function(sourceId, targetId, event){
// some code
return true;
});
The event is blockable. Returning false will prevent column dropping.