Drag&Drop: Only accept items with the same parent-parent group?

Drag&Drop: Only accept items with the same parent-parent group?

Hi everyone
I have to do a webapplication to create plans for our buildings (about usage, maintenance and some things)

So, for every  plan
-I have multiple room div items, which represents the rooms of a building.
Every room div contains 7 containers, one for each day. These containers are supposed to be the droppables, because they can contain multiple Items, which can be "usage", "cleaning", "maintenance" or something like that, that happen in this room on this day.

In HTML, it looks like this:

 <DIV id=room1 class=room roomId=a1>
     <ul id="monday1" class='day'>
        <li class="Item">1</li>
        <li class="Item">2</li>
        <li class="Item">3</li>
     </ul>




     <ul id="tuesday1" class='day'>
        <li class="Item">1</li>
        <li class="Item">2</li>
     </ul>
      to be continued... 
 </DIV>




Ok, the drag & drop works fine.
The problem is: The same room can appear multiple times on the same plan and dropping should only work on the same room.

In other words: If the div room1 and room5 are the same room (same roomId), all <li> Items in both room-divs should be drag&dropa ble between themselves.
Is this possible?