Getting the HTS number for each line item number
SCEM: -
1    SELECT [E1EVMTID-TRXID] - HAWBFCR Value
GTS: -
2  SELECT GUID_MOBJ FROM TABLE /SAPSLL/LEGDOC WHERE
      QALDOC = 'PDOC' AND
         PAPTY = 'ZDC008' AND
        PAPNO = PARAM_VALUE

3 SELECT PAPNO FROM TABLE /SAPSLL/LEGDOC WHERE
      QALDOC = 'PDOC' AND
         PAPTY = 'ZDC007' AND
        GUID_MOBJ =  [GUID_MOBJ FROM STEP 2].
4 Select LGREG from table /SAPSLL/LEGTPR
  where MANDT = SY-MANDT
           MOBJT = 'O'
   GUID_MOBJ = /SAPSLL/LEGDOC-GUID_MOBJ [from Step 3]
5 Get the numbering scheme (ex. ‘USHTS’)  for Tariff Codes from table /SAPSLL/TLEGSV ‘Leg. Srv.: Assign Tariff Systems to Legal Regulations’.

SELECT CTSIM from table /SAPSLL/TLEGSV where
     MANDT = SY-MANDT and
      SRVLL = ‘LECCUS’ and "Legal: Customs
6 SELECT GUID_CUIT from table SAPSLL/CUIT where
GUID_CUHD = /SAPSLL/LEGDOC-GUID_MOBJ [from step 3]
7 Table /SAPSLL/CORCTSC links the HTS number GUID to the Customs Shipment line items.

SELECT GUID_CTSNUMC from table /SAPSLL/CORCTSC where
          MANDT = SY-MANDT and
           POBJT = ‘02’ and (GTS: Customs Document - Item)
   GUID_POBJ = /SAPSLL/CUIT
8 Call function module /SAPSLL/CTSNUMC_DB_SGL_READ
Input Parameter 1: IS_PK-GUID_CTSNUMC = /SAPSLL/CORCTSC-GUID_CTSNUMC
Input Parameter 2:  IS_PK-MANDT = SY-MANDT
Input Parameter 3:  IV_MANDT = SY-MANDT
Output Parameter 1: Field ET_RESULT-CCNGN is HTS Numbe
9 Logic Required from GTS to get PO related to each HTS Number
10 Logic required to group the HTS Numbers by CPO
11 SELECT VBELV (Sales Order Number)
FROM VBFA
WHERE VBFA-VBELN = [MPO # found in from step 3]
             VBFA-VBTYP_V = "C"
12 SELECT BSTNK (CPO)
FROM VBAK
WHERE VBAK-VBELN = VBFA-VBELV (Sales Order Number)