TOPIC: Member Discount based on other than Registered

I am setting up DT Register for a client who wants all event bookers to register as users on the site but also have a different user category (perhaps authors) for those who are financial members. It wants to restrict member discounts to these financial members.

Is there any established non-hack way of having the member discount setting in an event look at a different user group to Registered?

If not, can anyone point me towards where the change of group id would need to be made in the code?

Thanks in advance.