Setting a Delivery Block on a Delivery during creation (VL01N)

Hi all,

We have a requirement to place a Delivery Block (Awaiting Inspection - QA) on Deliveries of a certain Order Type when they are created.

I've previously done this for Sales Order Header (via MV45AFZZ, USEREXIT_SAVE_DOCUMENT_PREPARE) by setting VBAK-LIFSK to 'QA'. This worked straight away.

However I'm having a real issue in doing something similar for Delivery Header. I've already attempted changes (via MV50AFZ1, USEREXIT_SAVE_DOCUMENT & USEREXIT_SAVE_DOCUMENT_PREPARE) by changing LIPK-LIFSK.

I wonder if I'm changing the wrong value, or setting it at the wrong point for Deliveries?

Any help much appreciated, cheers!