Dear Andy,
This is hardly can be done in VIP Team To Do List because it doesn't have Custom Fields. I mean there is no field "the day before the due date" in VIP Team To Do List.
However, you can do this in VIP Task Manager Professional (http://www.taskmanagementsoft.com/) that features Custom Fields. You can create a field that will automatically calculate the date before the due date and allow the program to include custom fields section into the emails.
Regards,
Serge