How to use the "sum of multiple credit applications" with different expiry dates, as customer credit

Product: Oracle Credit Management and Oracle Receivables

Our Business Requirement:

We provide the customers credit limits based on the bank guarantees. Most of the times, customers provide different bank guarantees; starting and expiring on different dates. At any time, customer's credit limit is always equal to the sum of the active bank guarantees' amount.

For example, customer A gives 2 different bank guarantees;

G1 for Rs. 50,000; Start Date: 01-Oct-2016;   Expiry Date: 20-Nov-2016

G2 for Rs. 100,000; Start Date: 10-Oct-2016;   Expiry Date: 31-DEC-2016

Every time, a bank guarantee is provided by the customer the customers credit limit is increased by the amount of this new bank guarantee.