FMDERIVE: adding a new MM source field

Question

Hi, I'd would to know how to add the field KNTTP (Account assignement category) in a derivation rule.
So far, I've done this steps:
1) Adding the field in the structure FMDERIVE inside de APPEND "AFMDERIVE"
2) Activating the user exit EXIT_SAPLFMDT_002
*--- Copy additional fields from the structure COBL.
MOVE-CORRESPONDING i_cobl TO c_fmderive.
*--- Copy additional fields from the structure COBL_AD
MOVE-CORRESPONDING i_cobl_ad TO c_fmderive.
3) Creating the new derivation rule in transaction FMDERIVE, like this:
SOURCE FIELDS: KNTTP (Account assignment category) & PLANT (Plant)
TARGET FIELDS: FUND_CENTER (Funds Center)
CONDITIONS: FM_AREA = XXXX & COMPANY_CODE = 1000 & KNTTP = A
Unchecked all in Attributes tab.
RULE VALUES = For example: PLANT = 1000 & KNTTP = A ==> FUND_CENTER = A
                                                  PLANT = 1000 & KNTTP = K ==> FUND_CENTER = Z
SAVE
But when I'm creating a purchase requisition (ME51N) and I choose the plant 1000 and the account assignment category A, the derivation is not working.
We have made a debugging and we've realised that the structure i_cobl doesn't have the field KNTTP, so the exit always move to a blank space in field KNTTP.
Anybody can help me? Is there a way to add fields in the i_cobl structure?? Should I use another User exit because the field belongs to MM??
If anybody have any other idea, I will be glad to read it!!
Thanks in advance!
Lorena

Answer 1

Hi, there is a way of using KNTTP in derivation (this also applies to other fields not available in COBL/COBL_AD), not sure if it is a recommended approach because it requires reading the values from memory, it does work though.
Read the value of KNTTP from memory and assign it to C_FMDERIVE in EXIT_SAPLFMDT_002, include ZXFMDTU02. then it is available in derivation as source field, provided that you have added it to the structure. See code below:
DATA: lv_field(100) TYPE c.
FIELD-SYMBOLS: <ekpo> TYPE ekpo.
CONCATENATE '(SAPLMEPO)' 'EKPO' INTO lv_field.
ASSIGN (lv_field) TO <ekpo>.
IF sy-subrc = 0.
   c_fmderive-usertemp1 = <ekpo>-knttp.
ENDIF.