assigning more than one G/L account to transaction key WRX

Can any one tell me where we can create General Modification keys in MM-FI integration

As i need to assign more than one GL account for transaction key WRX (GR-IR)Clearing account.

There may be one valuation grouping code with different General modifications thereby we can assign more than one G/L account to WRX transaction key.

Example:

Valuation grouping code or valuation modification = IN

General Modifications: I01,I02,I03,I04..

General Ledger Accounts: 240940000,240940001,240940002,240940003

IN I01 240940000

IN I02 240940001

IN I03 240940002

IN I04 240940003

But , I am unable to find, where we can define these general modifications ( I01,I02,I03)....

If any one knew please let me know...

Ramesh B