Have modified code check this one.
TABLES MARC.
TYPE-POOLS: SLIS.
SELECTION-SCREEN BEGIN OF BLOCK A WITH FRAME TITLE TEXT-001.
PARAMETERS : M_MATNR TYPE MARC-MATNR OBLIGATORY ,
W_WERKS TYPE MARC-WERKS.
SELECTION-SCREEN END OF BLOCK A.
TYPES: BEGIN OF TYP_MARC,
MATNR TYPE MARC-MATNR ,
WERKS TYPE MARC-WERKS,
END OF TYP_MARC.
TYPES: TT_MARC TYPE TYP_MARC.
DATA: IT_MARC TYPE TABLE OF TT_MARC,
IT_MDPSX LIKE TABLE OF MDPS,
IT_FCAT TYPE SLIS_T_FIELDCAT_ALV.
DATA: WA_MARC TYPE TYP_MARC,
WA_FCAT TYPE SLIS_FIELDCAT_ALV.
DATA : IT_FIELDCAT_ALV TYPE TABLE OF SLIS_FIELDCAT_ALV,
IT_FIELDCAT TYPE SLIS_T_FIELDCAT_ALV,
WA_FIELDCAT_ALV TYPE SLIS_FIELDCAT_ALV,
WA_LAYOUT TYPE SLIS_LAYOUT_ALV . " FIELDCAT DECLARATION
DATA : LV_MATNR LIKE MARC-MATNR,
LV_WERKS LIKE MARC-WERKS.
LV_MATNR = M_MATNR.
LV_WERKS = W_WERKS.
START-OF-SELECTION.
PERFORM FILL_STOCK.
PERFORM FIELDCAT.
PERFORM DISPLAY_DETAILS.
FORM FILL_STOCK.
CALL FUNCTION 'MD_STOCK_REQUIREMENTS_LIST_API'
EXPORTING
MATNR = LV_MATNR
WERKS = LV_WERKS
TABLES
MDPSX = IT_MDPSX
EXCEPTIONS
MATERIAL_PLANT_NOT_FOUND = 1
PLANT_NOT_FOUND = 2
OTHERS = 3
.
ENDFORM.
DEFINE FIELDCAT .
WA_FCAT-COL_POS = &1.
WA_FCAT-FIELDNAME = &2.
WA_FCAT-TABNAME = &3.
WA_FCAT-SELTEXT_M = &4.
* WA_FCAT-EDIT = &4.
APPEND WA_FCAT TO IT_FCAT.
CLEAR WA_FCAT.
END-OF-DEFINITION.
FORM FIELDCAT .
FIELDCAT '1' 'MDMAT' 'IT_MDPSX' 'Material' ."
FIELDCAT '2' 'MDWRK' 'IT_MDPSX' 'Plant' ."
WA_LAYOUT-ZEBRA = 'X'.
WA_FIELDCAT_ALV-NO_ZERO = 'X'.
WA_LAYOUT-colwidth_optimize = 'X'.
APPEND WA_FCAT TO IT_FCAT.
CLEAR WA_FCAT.
ENDFORM.
FORM DISPLAY_DETAILS.
CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
EXPORTING
I_CALLBACK_PROGRAM = SY-CPROG
IS_LAYOUT = WA_LAYOUT
IT_FIELDCAT = IT_FCAT
TABLES
T_OUTTAB = IT_MDPSX.
ENDFORM.