How to get 3rd storage unit type in WM

I have a requirement like that

This enhancement will determine the Storage Unit Type in WM when a Storage Unit is created in WM.In pure WM the Storage Unit
Type is determined from the palletization data in the Material Master (Warehouse View 2):

During the Goods receipt the storage Unit types are determined via the User -Exit MWMTO007 with the following logic:

-->if qty of transfer order LTAP-VSOLM = MLGN-LHMG1 then SUT = MLGN-LETY1
-->if qty of transfer order LTAP-VSOLM = MLGN-LHMG2  then SUT = MLGN-LETY2
-->if qty of transfer order LTAP-VSOLM = MLGN-LHMG3  then SUT = MLGN-LETY3

i am using User-Exit MWMTO007 (Function exit EXIT_SAPML03T_002). I found the changing parameter LETY1 (1st storage unit type) and LETY2 (2nd storage unit type). But i was not able to find LETY3 (3rd storage unit type).

Can anybody help me out? i checked the other user-exits to find the field, but was not success.