How do I transfer a custom field Value from sd sales order created from VA01 to FI tables BKPF and BSEG.

The custom field is present and appended in VBAK ,VBAP ,BKPF and BSEG.

What process I need is when VF01 is run then the above populating of the custom field should happen

What should I do and achieve this

User exits? BAdI? Pls suggest