Hi
In standard, SAP will create the Sales Order and it will be blocked. However, you requirement is to that sales order should not be created for Div A in which the customer is blocked and you should get a warning or error message. You can try for an enhancement, in case you are using FSCM credit management. The BADI, implementation UKM_CHECK_STEP should help you in doing that
Regards
Sanil Bhandari