Custom processing for Projects workflow

Hi,

For Projects, we want to use custom notification functionality for workflow events. We cannot use agents

assignment nor data from HR as we don't have HR data in SAP. What we want to do the following for all events related to projects.

1. Users will choose the role to which they want the workflow/notification to go and click on SAVE for any action projects.

2. At this time,we want to call a custom function module to get the details of the recipients for that event and role from custom tables.

3. Using the above recipients list, we will send the alerts/notifications.

Please let me know if there is a place where I can assign the custom function module which gets executed after the event is triggered or when user clicks on save after assigning the role.

Thanks,

Sudheer