Restriction on Creation of Billing document

Hello Experts,

My requirement is liek below

1)     For delivery notes where goods issue is already posted and if Cost of goods sold is more compared to sales price, then billing document creation should not be allowed. (For delivery-related billing). System to populate a suitable error message accordingly. (Exclude free of charge items and other cases)

2) Here certain people should be excluded  and still be allowed to do create biiling document even if above control measures are implemented.

Also note that we need the above restriction for "VF01" & "VF04" Transactions. Kindly advice on how to achieve the above requirement.

Regards,

Amit K S