Insert Items to Order Base based on Refnum?

Hi,

Is there an out of the box functionality where by I can insert a 'group' of items to an incoming Order Base via Integration based on, say a Refnum?

I know Auto Assignment rule has it's limitations where I cannot assign default items to OB.

I can do so via Loop Back Transmission logic where by I can trigger an agent to send me a OB XML based on a given condition.

Any other option would be helpful.

Thanks,
Vikram