How to exclude certain order types from credit check calculation?

How can we exclude specific order types from credit check calculation? For example, customer has booked orders of 2,000,000. 750,000 are of the order type we want excluded. Customer's credit limit is 1,500,000. So when we enter a new order for 100,000 we want this customer to pass credit check because 1,250,000+100,000 is under their credit limit.  What is currently happening is the order goes on hold because the total amount of booked orders is 2,000,000. 

Note: I'm not asking how to turn credit checking off for specific order types.  I'm asking how to get certain order types excluded from the credit checking calculation.

Thanks very much for your input!