Sales Rep vs Admin Activity Permissions?

Sales Rep vs Admin Activity Permissions?

Our sales reps were unable to see the Admins activities that were entered in the client record, but they were able to view other sales reps entries.  I went into Data Sharing Settings and changed the "Activities" status to Public Read/Write/Delete.

I don't want the reps to be able to edit or delete any activity that wasn't created by them or assigned to them.  They should only be able to view activities that were created by their predecessor.  Is there a way to do this?

Thanks,
Kathleen