How to increase & print serial no in report Navision 4.0

Hi All,

I entered same item 2 or 3 times in purchase order as per below image:-

1805.P_Line.JPG

now i create report with group footer to print each single item with sum of qty as per below images:-

report displaying everything fine but s.no is showing like 3, 9, 16 instead of correct serial nos 1, 2, 3 and i also tried to increase srno at onaftergetrecord(), onpresection() & onpostsection() but all is fail, it is not showing correct s.no.

Pls help me & tell me how i can print right s.no .

Thanx

kamal