Refresh data in ALV OO - URGENT

Hi experts!

I'm doing an on line program that uses an ALV OO with a dinamic fieldcat..

When I use the method o_alv1->set_table_for_first_display the fieldcat has three colunms and I create a dinamic table with 3 colunms and no data... After this I set some options in my program that select the data I need and it can increase the number of colunms of my ALV OO... So I redo the fieldcat and and create a dinamic table with the colunms necessary...

I use the following code to refresh my ALV:

CALL METHOD cl_gui_cfw=>flush.

CALL METHOD o_alv1->set_frontend_fieldcatalog

EXPORTING

it_fieldcatalog = t_fieldcat1.

CALL METHOD o_alv1->refresh_table_display.

SET SCREEN 0.

LEAVE SCREEN.

My problem is when I back to the ALV screen the colunms are right but the data does not appear!

My table is a <fs_data> type standard table.

Can Anyone Help me???

Thanks in advance!

Gabriel