FBCJ Business area assignment

Our requirement is in FBCJ of Business area :M001 we want to book the expenses of another business area M002 (Cross business area transaction). But since cash is a backend transaction we cannot give any business area . So the system automatically picks up the business area of the expense to cash which is actually wrong. . Please help us how to resolve this issue. Is there any other way to put business area to cash GL . please explain.

regards

sree