Hi Anshika,
As per my understanding,your smartform will display sales order details for a customer number.That means there is window for displaying customer details and another table in smatform for displaying sales orders under that customer.
Get the customer details into IT_KNA1
then collect the sales orders from VBAK for all entries in IT_KNA1 where KUNNR = it_KNA1-KUNNR.
loop through IT_KNA1 into wa_kna1
read IT_VBAK into it_vbak_fm with key kunnr = it_kna1-kunnr.
call smartform FM
exporting
wa_kna1= wa_kna1
tables
it_vbak = it_vbak_fm.
endloop.
Regards
Pallavi Koora