ABAP nach Excel mit Formel, aber wie?

Code: Alles auswählen.

*&---------------------------------------------------------------------*
*& Report ZDEMA_TEST84
*&---------------------------------------------------------------------*
*&
*&---------------------------------------------------------------------*
REPORT zdema_test84.
INCLUDE ole2incl.
DATA: excel    TYPE ole2_object,
      workbook TYPE ole2_object,
      sheet    TYPE ole2_object,
      zelle    TYPE ole2_object.
DATA: zeile  TYPE i. "Zeile. Wird zur Laufzeit gesetzt
DATA: spalte TYPE i VALUE 1. "immer in Spalte 1
DATA: sy_tabix LIKE sy-tabix.

TYPES: BEGIN OF ty,
         value(30) TYPE c,
       END OF ty.
DATA:wa TYPE ty.
DATA:itab TYPE TABLE OF ty.

START-OF-SELECTION.

  wa-value = '1'.
  APPEND wa TO itab.
  wa-value = '=wenn(A3="2";"X";"")'.
  APPEND wa TO itab.

  CREATE OBJECT excel 'excel.application'.
  SET PROPERTY OF excel 'visible' = 1.
  CALL METHOD OF excel 'Workbooks' = workbook.
  CALL METHOD OF workbook 'Add'.
  CALL METHOD OF excel 'Worksheets' = sheet
  EXPORTING #1 = 1.

  CALL METHOD OF sheet 'Activate'.
  SET PROPERTY OF sheet 'Name' = 'Test1'.

  LOOP AT itab INTO wa.
    sy_tabix = sy-tabix. "Call method of sheet setzt sy-tabix neu
    zeile = sy-tabix.
    CALL METHOD OF sheet 'Cells' = zelle
                EXPORTING #1 = zeile
                          #2 = spalte.
    IF sy_tabix = '1'.
      SET PROPERTY OF zelle 'Value' = wa-value.
    ELSE.
      SET PROPERTY OF zelle 'FormulaR1C1' = wa-value.
    ENDIF.
  ENDLOOP.