This event calls user-defined handlers (if there are any) and passes the following parameters:

• dId - id of the dragged item;
• lId - id of the potential drop landing;
• sObject - source object;
• tObject - target object.

          tree.attachEvent("onDragIn", function(dId,lId,id,sObject,tObject){});
 

This event returns:

true - allows drop;
false - denies drop.