Hi,
I agree with Swanand about standard process.
Having said that, I would advice to you to play around with Copy Controls > Sales Document to Sales Document at Item Category level there is a provision to use a check box which says - Update Document Flow.
Check if that could serve your purpose.
Swanand:
In some cases say for example, you may have a scenario where you just want to copy a Sales Order into another one only to avoid creating an order with say 100 line items a simple copy from one sales order to another will help. There you may not want the Original Sales Order to reflect in the document flow.
Thanks.