Hi Arie,
Modify the code as below
DATA : table TYPE REF TO data.
FIELD-SYMBOLS <table> TYPE table.
FIELD-SYMBOLS <wa> TYPE any.
FIELD-SYMBOLS <LV_VALUE> TYPE ANY.
CREATE DATA table TYPE TABLE OF STRUCT_TYPE.
APPEND INITIAL LINE TO <table> ASSIGNING <wa>.
IF <wa> IS ASSIGNED.
ASSIGN COMPONENT 'CATEGORY' OF STRUCTURE <wa> TO <lv_value>.
IF <LV_VAlUE> IS ASSIGNED.
<LV_VALUE> = 'CAT1'.
ENDIF.
ASSIGN COMPONENT 'SERIES' OF STRUCTURE <wa> TO <lv_value>.
IF <LV_ValUE> IS ASSIGNED.
<LV_VALUE> = '1'.
ENDIF.
ENDIF.
"Similarly you can append record by record
Hope this helps you.
Regards,
Rama