Hi Venkat,
How many rows in itab2, then itab1 will have same number columns?
First create a dynamical itab1 with itab2`s rows.
Then,
Loop at itab2.
CONCATENATE 'FW' sy-tabix INTO lv_fieldName.
ASSIGN COMPONENT lv_fieldName OF STRUCTURE <s> TO <FS>.
Endloop.
regards,
Archer