Aca un ejemplo, copia el codigo y pruebalo..!!
REPORT ZPRUEBA_ALV_DINAMICO.
TYPE-POOLS: slis.
FIELD-SYMBOLS: <t_dyntable> TYPE STANDARD TABLE, " Dynamic internal table name
<fs_dyntable>, " Field symbol to create work area
<fs_fldval> type any. " Field symbol to assign values
PARAMETERS: p_cols(5) TYPE c, " Input number of columns
p_rows(5) TYPE c.
DATA: t_newtable TYPE REF TO data,
t_newline TYPE REF TO data,
fs_fldcat TYPE slis_t_fieldcat_alv,
t_fldcat TYPE lvc_t_fcat,
wa_it_fldcat TYPE lvc_s_fcat,
wa_colno(2) TYPE n,
wa_flname(5) TYPE c.
* Create fields .
DO p_cols TIMES.
CLEAR wa_it_fldcat.
move sy-index to wa_colno.
concatenate 'COL'
wa_colno
into wa_flname.
wa_it_fldcat-fieldname = wa_flname.
wa_it_fldcat-datatype = 'CHAR'.
wa_it_fldcat-intlen = 10.
APPEND wa_it_fldcat TO t_fldcat.
ENDDO.
* Create dynamic internal table and assign to FS
CALL METHOD cl_alv_table_create=>create_dynamic_table
EXPORTING
it_fieldcatalog = t_fldcat
IMPORTING
ep_table = t_newtable.
ASSIGN t_newtable->* TO <t_dyntable>.
* Create dynamic work area and assign to FS
CREATE DATA t_newline LIKE LINE OF <t_dyntable>.
ASSIGN t_newline->* TO <fs_dyntable>.
************************
** Populate internal table
************************
DATA: fieldname(20) TYPE c.
DATA: fieldvalue(10) TYPE c.
DATA: index(3) TYPE c.
DATA: index2(3) TYPE c.
DO p_rows TIMES.
index2 = sy-index.
DO p_cols TIMES.
index = sy-index.
MOVE sy-index TO wa_colno.
CONCATENATE 'COL'
wa_colno
INTO wa_flname.
* Set up fieldvalue
CONCATENATE 'VALUE ' index '-' index2 INTO
fieldvalue.
CONDENSE fieldvalue NO-GAPS.
ASSIGN COMPONENT wa_flname
OF STRUCTURE <fs_dyntable> TO <fs_fldval>.
<fs_fldval> = fieldvalue.
ENDDO.
* Append to the dynamic internal table
APPEND <fs_dyntable> TO <t_dyntable>.
ENDDo.
************************
** Display internal table
************************
DATA: wa_cat LIKE LINE OF fs_fldcat.
DO p_cols TIMES.
CLEAR wa_cat.
MOVE sy-index TO wa_colno.
CONCATENATE 'COL'
wa_colno
INTO wa_flname.
wa_cat-fieldname = wa_flname.
wa_cat-seltext_s = wa_flname.
wa_cat-outputlen = '10'.
APPEND wa_cat TO fs_fldcat.
ENDDO.
* Call ABAP List Viewer (ALV)
CALL FUNCTION 'REUSE_ALV_GRID_DISPLAY'
EXPORTING
it_fieldcat = fs_fldcat
TABLES
t_outtab = <t_dyntable>.