Create Actor filter to delegate a task

Hello.

I have 2(X & Y) actors defined in my organization and 3(A,B,C) groups

The first task is assigned to the actor X mapped to Group A

The Second task is assing to actor Y mapped to Groups B & C

What want is that when the second task is for first time available to be assigned to group B, and then if the guy who is working on the task wants to delegate the work i want him to be able to choose the user form the group C to delegate it

I have no idea how to do this, and have no expirience on how to configure the actor filter.

so, where is the information to know wich clases i have to import to get:
1-Users
2-Groups
3-Actors
4-Tasksid

I think that info is what i need to construct the script to filter the actors, but i dont know exactly how to do it and probably i'm missing something.

Thanks for your time.