Validation for internal order depending on cost center

Requirement:

In FI posting, users want to post an expense for internal order and they want the cost center must be validated.
For ex:
Internal order : from 100002 to 100005
Cost center: Null

Steps:

1. T-code GS01

Create Set for Internal Order

In Basic data, input table for IO: AUFK
Next, input field name: AUFNR - IO number

2. T-code GGB0:

Before doing this step, you need to define the Message ID beginning with Z

Click on button Step:

Prerequiste: "key field" IN "setname (from GS01)"

Check: "check field" = cost center

If not: Message XYZ


One validation step for each set of internal orders.

If you want to make just one validation step, define a Z-table where you enter the allowed combinations of internal order sets + cost center.
Use this Z-table in a validation user-exit.