User Exit for extended ORDERS05

Hello,

We have extended tables VBAK & VBAP, and I have to put these new fields into the outbound ORDERS05 when a sales order is created.

I have extended the IDOC with some custom segments, but I can't seem to find the USER EXIT or BADI or NAST function module (SAP R/3 Enterprise) - can someone please point me in th right direction?

Many thanks!