Credit Check for Finance document posted in FB70

Dear SAP Experts,

We have requirement to stop customer document posted in FB70 if the credit limit exceeds. I have maintained Credit limit with high risk which blocks delivery from sales end, for which the settings maintained in OVA8.

If we post anything in FI using FB70 it gives only the warning message but our requirement is to stop the postings, I tried to stop from message control for the message class but of no help.

I have another issue; Needs to stop postings for specific GL if the GL balance reaches negative.

I would be very happy if some one help me in this regard.

Thanks,

Lokesh