Implementing different levels of drag/drop functionality?

I'm working on a tablet app for a motel. Initially, the app was going to be tested on one floor. Essentially, the app would be used to move guests from one room/bed to another room/bed.

As you can see from the very simple screenshot, I can drag/drop Joe from Room 301-#1 to Room 303-#2. Or I can drag/drop Joe within Room 301: From #1 to #2. Overall, in the tablet you can see every room from one floor. In here, it works great.

The issue now is that the app will be used for several floors. I really like the drag/drop functionality, but I don't know how I can drag/drop from different floors. For example, let's say I want to drag/drop Joe from Room 301-#1 to Room 404 #2. How can I show that graphically using this drag/drop interface.

I'm trying to find creative ideas that can be used for this. It needs to be simple, and as simple as it may sound, it would be to move Joe from his current room 301 #1 to room 405 #3 with just one movement/swype.

Thanks.