Can Credit Limit be set at Parent Level for a parent and children?

We have a customer, John Doe, who we presently do business with in our Agricultural sales, which is the predominance of his activity. John Doe also wants to engage us in some Mining sales. What we are wanting to do is setup a new child Address Book record to handle the Mining sales (we use a Cat Code to determine sales sector), but we want the Credit Limit to still be at the Parent Agricultural sales Customer Master record, since it is still the same person, and any invoices created for either Customer to check against the Parent credit limit.