Помогите разобраться как в одну ячейку засунуть только один элемент

[Sadist_dead]

Вот сделал перемещения дива по таблице, но проблема в том что не могу понять как сделать так чтобы в ячейку таблице можно было добавить только один элемент (див)??

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        // Only called when element is dragged over the a dropzone with the same ddgroup
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                // Remove the invitation
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            //this.el.highlight();
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        },
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        // Called upon successful drop of an element on a DDTarget with the same
        onDragDrop : function(evtObj, targetElId) {
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            var dropEl = Ext.get(targetElId);

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            else {
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    };

    // Configure the cars to be draggable
    var carElements = Ext.get('cars').select('div');
    Ext.each(carElements.elements, function(el) {
        var dd = new Ext.dd.DD(el, 'carsDDGroup', {
            isTarget  : false
        });
        Ext.apply(dd, overrides);
    });

    var truckElements = Ext.get('trucks').select('div');
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    //Instantiate instances of Ext.dd.DDTarget for the cars and trucks container
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    //Instantiate instnaces of DDTarget for the rented and repair drop target elements
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    var repairDDTarget = new Ext.dd.DDTarget('repair', 'carsDDGroup');

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    rentedDDTarget.addToGroup('trucksDDGroup');
    repairDDTarget.addToGroup('trucksDDGroup');


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