How to create a validation rule in SAP BODS Job

Hi Experts

I have created a BODS Job and in that job i have to create a validation rule as if the cust_id is null the loading must stop.

I dont have idea where i have to define this validation rule in the Job and how to stop the load job if the validation rule file.

My Job was defined like below image

Please guide me where i have to define the validation rule and how to stop the load job.

Thanks in advance

PrasannaKumar