Teaching with Moodle

Hello,

I teach Language on moodle.

Let me explain my quesiton by saying an example:

Imaging that the text book of a course is Interchange1 .

And so many students can will be registered in that course.

But practically, we can hold Voice Conference classes for 10-15 of them in specific times.
For example some of them may be able to come to our online classes just in Mondays and Wednsday at 4:00 PM to 6:30 PM
The others may want the other days and other time online classes.

So the students might be devided into many different groups of 10-15 and each group has its own time for comming to online class.

Is there any way I can have this in the same course?

Creating multiply courses for the same book is really a big mess.

However, the students of group A should not be able to participate in Online classes of group B.

However, they can be in the same course and use the same materials.

on the registration. I should be also to enroll them into different groups.

Is there any way? If there is a way. Please teach me how I can do it.

Thanks,