Splitting line item in Sales Order-VA02

Hello All,

I got struck with the below requirement, Can someone share their ideas, if any one come across such case.

Requirement : If ordered material obsolete then system has to propose follow up material ( which will be maintained in MMR-MRP4 view - Followup material field) based on stock availability.

We have done the same by using USEREXIT in Sales order creation & working fine without any issues.

But, If stock partially exists for entered material, then new line item has to add/insert with the follow up material.

Eg;

M1- stock -30 ea

M2- No stock ( Follow up material)

*In Sales Order Creation- VA01,*

Line Item -- Material - Ordered Qty

M1 - 50 Qty (ordered qty)

Result;

Line Item -- Material - Ordered Qty - Item Cat

10----M1-----30 ea - TAN

11----M2--

20 ea - TAB ( MTO)

Working fine-

We are able to do it during Sale Order creation (VA01).

*Change mode of Sales order - VA02;*

Line Item -- Material - Ordered Qty - Item Cat

10----M1-----30 ea - TAN

11----M2--

20 ea - TAB ( MTO)

if user increases the M1 qtty to 10 Ea, then system should behave as shown in below eg,

Line Item -- Material - Ordered Qty - Item Cat

10----M1-----30 ea - TAN

11----M2--

20 ea - TAB ( MTO)

12----M2--

But We are facing problem during Change mode .

in VA01- (Sale order Creation), the logic was written in exit : USEREXIT_MOVE_FIELD_TO_VBAK - which is working fine

During Change(VA02), above exit will not be useful. Hence tried to use exit : USEREXIT_MOVE_FIELD_TO_VBEP.

But not able to add new item at this level.

All useful ideal will be appreciated.