How to input absent classroom
You can input absent classroom the same way as absent teacher:
Once inputted the software show the lesson's for which you have to find another room. These are shown in different color then the regular substitutions:
The right side shows the rooms that can be used. You can pick the room by double click in the right list.
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In version 2010 or before:
Missing classrooms
Again, the same way is used to add the missing classroom:
Since some action is required when the classrooms is missing(children cannot be in it), the software add new lines into the substitutions and you have to select a different classrooms for these:
In the right panel you can see the available classrooms that can be selected for this lesson. 
Once you select some classrooms a dialog appears where you can see that you have just changed the room from s106 to s110:
Notes
- the "classroom" lines have different color
- you can still cancel this lesson, move or or change the subject 
- at the top there are classrooms this lesson can be in. So it can happen that some occupied rooms are in the list above the free rooms, because the lesson was not allowed to be in this room in the timetable software during the timetable creation.
 
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