How to add constraints of below mentioned queries

[Avijit Paul]

Hello

I want to know how to add constraints of the below mentioned queries:

1) 1 Classroom have 2 sets of student. I want to have least 2 hours of continuous class of any set of students before changing the classroom of the students.   
 At present, sometimes after every one hour set of students is changing in the classroom which creates practical problems.

[Liviu Lalescu]

Hello,

The existing room changes constraints are not enough?

A customization could be possible, but it looks complicated.