Inbound delivery idoc LAVA with same HU as outbound delivery

Hi,

We are creating an inbound delivery IDOC from an outbound delivery based on delivery type LF with message type LAVA. We are trying to send the same handling unit from the outbound delivery and this is where the error occurs.

The inbound idoc fails with error code HUFUNCTIONS 031 = number range interval doesn't exist in HU_VEKP.

If we add the HU in transaction VL32n (dialog) it works just fine.

Any ideas how we can solve this?

We aren't using stock transfers and SPED, because we're creating purchase orders that send ORDERS and are then confirmed with ORDERSP.

Do you think we could add the HU in the save routine in include MV50AFZ1 using a function module that is called in a background task?

Thanks in advance,

Amber