Adopt PR to PO BADI or User Exit

Need advise if there any one exprience on creating User Exit or BADI for adopting PR to PO (ME21N) .

I create custom tab for both PR (ME51N) and PO (ME21N), what i need to do when adopting PR to PO the customer tab value not copied even its field name are the same.

Need expert advise on this if there is any BADI or User Exit i can used to copied over the custom tab value.

Thanks