activities must not be on the same time on different days

[bachiri401]

what is the constarint used to make act1 and act2 OF the same students and of the same teacher and of the same subject not to come on the same time on different days; for example we have "maths'' for group "a" it is divided ito three sessions. we need each session to be on an hour fidderent from the others enen they are on different days

[Volker Dirr]

Please have a look at https://www.youtube.com/watch?v=QOgkTMSAoEM (your question starts at around 01:30 in the video)

[bachiri401]

thanks that's very kind of you.