Hello Rudi,
use either of below approach...
APPROACH--> 1
FIELD-SYMBOLS:<RESULT_FIELDS_1> TYPE _ty_s_TG_1.
data: IT_RESULT_PACKAGE TYPE STNADARD TABLE OF _ty_s_TG_1,
lv_index type sy-index.
IT_RESULT_PACKAGE[] = RESULT_PACKAGE[].
DELETE RESULT_PACKAGE WHERE stkeyfig = 'cs149' .
DELETE RESULT_PACKAGE WHERE stkeyfig = 'cs158' .
DELETE IT_RESULT_PACKAGE WHERE stkeyfig <> 'cs149'
OR stkeyfig <> 'cs158'.
SORT it_result_package by CREDITOR MATERIAL acending STKEYFIG decending.
lv_index = 0.
LOOP AT it_result_package ASSIGNING <result_fields> FROM lv_index
WHERE <result_fields>-stkeyfig = 'CS158' .
lv_index = sy-index + 1 .
LOOP AT it_result_package ASSIGNING <result_fields_1> FROM lv_index.
IF <result_fields_1>-stkeyfig = 'CS149' AND
<result_fields_1>-CREDITOR = <result_fields>-CREDITOR AND
<result_fields_1>-MATERIAL = <result_fields>-MATERIAL.
<result_fields_1>-VALUE_LC = <result_fields>-VALUE_LC .
ELSE.
<result_fields_1>-VALUE_LC = 0.
exit.
ENDIF.
ENDLOOP.
lv_index = sy_index.
ENDLOOP.
APEEND LINES OF it_result_package TO table RESULT_PACKAGE.
CLEAR : it_result_package.
----------------------------------------------------------------------------
APPROACH--> 2
DATA : RESULT_PACKAGE_CS149 TYPE STNADARD TABLE OF _ty_s_TG_1,
RESULT_PACKAGE_CS158 TYPE STNADARD TABLE OF _ty_s_TG_1.
FIELD-SYMBOLS:<RESULT_FIELDS_CS149> TYPE _ty_s_TG_1,
<RESULT_FIELDS_CS158> TYPE _ty_s_TG_1.
IT_RESULT_PACKAGE_CS149[] = RESULT_PACKAGE[].
IT_RESULT_PACKAGE_CS158[] = RESULT_PACKAGE[].
DELETE RESULT_PACKAGE WHERE stkeyfig = 'cs149'.
DELETE RESULT_PACKAGE WHERE stkeyfig = 'cs158'.
DELETE RESULT_PACKAGE_CS149 WHERE stkeyfig <> 'cs149'.
DELETE RESULT_PACKAGE_CS158 WHERE stkeyfig <> 'cs158'.
SORT RESULT_PACKAGE_CS158 BY CREDITOR MATERIAL.
LOOP AT RESULT_PACKAGE_CS149 ASSIGNING <RESULT_FIELDS_CS149>.
READ TABLE RESULT_PACKAGE_CS158 ASSIGNING <RESULT_FIELDS_CS158>
WITH KEY <RESULT_FIELDS_CS158>-CREDITOR = <RESULT_FIELDS_CS149>-CREDITOR
<RESULT_FIELDS_CS158>-MATERIAL = <RESULT_FIELDS_CS149>-MATERIAL BINARY SEARCH.
IF sy-subrc = 0 .
<RESULT_FIELDS_CS149>-VALUE_LC = <RESULT_FIELDS_CS158>-VALUE_LC.
ENDIF.
ENDLOOP.
APPEND LINES OF RESULT_PACKAGE_CS149 TO RESULT_PACKAGE.
APPEND LINES OF RESULT_PACKAGE_CS149 TO RESULT_PACKAGE.
FREE: RESULT_PACKAGE_CS149[] , RESULT_PACKAGE_CS158[].
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NOTE: For either approch u need to set Semantic grouping @ DTP Level on Fields : CREDITOR & MATERIAL.
for approach 2 u may required nothing to change.. but i will suggest approach 1 for performance (may require little chnages).....
Regards,
Hitesh