Trigger a workflow when user added to permission group

Question

I'm not sure if this is even possible so here goes:

I have a calendar list. After creation of the list I will add a choice field to the list in an event receiver where the choices will be the email addresses of the users in a permission group of the site. Here is my quandary, I need a way to remove/add addresses when the membership of the group changes. I was initially thinking a workflow but not sure how to trigger it, the only way might be to manually trigger the workflow. There may be a better way than using workflows. Any suggestions on how to approach this?

Answer 1

There are no event receivers which fire when users are added or removed from SharePoint groups. List events don't fire on the User Information List. The best bet would be to develop a timer job which reads the audit log for the site to determine which groups have been updated, then fire a workflow or code from that.