Required item no: to populate custom field while creating item for a Sales order

Hello Experts,

I have created a custom field for item data of sales order using AET .

I want to populate this field automatically when ever we create a new item for a sales order using UI or CRMD_ORDER or WCEM by concatenation Sales order number and item number.

We are getting Item GUID but not getting the item number(need item number before getting saved is their any chance to get item number from item GUID ) to populate the field and save it.

For this we tried using BADI's

CRM_BTX_EXTENSIONS

CRM_ORDERADM_I_BADI

Thanks in advance,

Manasa Veena P.