Change the order of item code in invoice

SOLVED

Hi all,

I want to change the order of the item code appears on the SO invoice.

I have tried something like this 

line.PrintSequenceNumber = printSeqNo; //where printSeqNo is already set

and on the report I set to order by PrintSequenceNumber.

but after posting the SO, the PrintSequenceNumber has different value. How do I make the initial value of PrintSequenceNumber (that I set) permanent after posting?

thank you