Reaction field changing from error to warning is also not acceptable as it will work for all cases irrespective of customer has balance or not. User can play with it. My Business is not allowing this.
If this is the case,then follow the below steps.
1. As already suggested,define new risk category for this kind of customers and maintain the C (warning message) in OVA8 against the Dynamic credit check, so that you can approve it the blocked document.
or if you want to follow the existing process only with out defining new risk category follow the below one.
2. Respective business user(Credit manager) can increase the credit limit for this customer.This can be work around solution and if the business is okay every time following this process of increasing the credit limit when this kind of situation arises then you need not follow the first one.
thanks,
Srinu.