You can query the users of a role with the following public API:
ivy.wf.getSecurityContext().findRole("Everybody").getAllUsers();
Then you can draw a process that loops over a task switch and creates new user tasks until all users have one.
The second task is a system task which continuous the execution until the list of users is empty.
![alt text][1]
[1]: http://answers.axonivy.com/upfiles/createTaskForEachUser.png