Group Tasks Notify SharedBy users

System

Hi,
I have an external task which calls iwsend_servlet_mail.ipl. The next task is a group task. I want to notify all the users in the group task. How can I get this information? When I do task->GetOwner, I do not get a owner because no one has taken ownership yet.
Here is my system info is:
Host OS: SunOS (5.8)
Version: 5.5.2 Build 14136 Interwoven 20021127