Need pass shipment number to AR eff field

Hi team,
We have an requirement, where we need to pass shipment number from sales order to AR invoice.

Specifically for few BU's.

We have went through few docs where we can use service mappings and algorithms but those contains steps to achieve OM eff to AR dff.

Our requirement is to use standard shipment field and pass the shipment number to AR dff field for specific BU's.

Please let us know.

Thanks,
Sandhya