RELATED TO ALV GRID

hi all,

In alv reports which r done using object oriented concepts, im able to print all the fields

of a table by passing LFA1 table to the parameter I_STRUCTUE_NAME of method

SET TABLEFOR_FIRST_DISPLAY and IT_OUTTAB as ITAB.

I declared ITAB as...DATA:ITAB TYPE TABLE OF VBAK .

Now, the problem is...if i want to declare my ITAB with only few fields then wat is the method i have to use to display and wat r the parameters i have to pass...so that my output will have only the columns i declared and not the whole structure of LFA1.