How do I filter Order Reason by Doc Type in Lean Order?

Hi,

I am not sure this is the right forum, but I have a requirement to filter Lean Sale Order (LORD) - Order Reason by Doc Type.   Where do I begin?   I can see all the Order Reason in the drop down list in LORD, I did a F2 on that field to get all the tech information, but where do I start?   Please advise.

I am very new to SAP and to CRM land.   I have search thru many blog and I have tried what's described in Enhancing SAP Lean Order Management for SAP Retail Part 1 | SAP Experts:Consulting & Integration - DataXstream

with the following steps:

SM30 - Change the LORD_MAPPING - HEAD AUGRU to use my own ZH_TVAU, own search help exit.  but it doesn't seems to go into the search help exit at all.  Am I missing something or those are old information. 

Thanks in Advance!