Hi
if the previous code doesnt work, use on change instead of at new.
sort it_final by vbeln posnr.
loop at it_final into wa_final.
wa_final-orderqty = 0.
wa_final-netvalue = 0.
on change of wa_final-posnr.
coninue.
endon.
modify it_final from wa_final index sy-tabix.
endloop