How to manage Document no while import sales order ?

Hi Expert ,

     I have created a xml format file using .net.This xml format is below 

<Root>

<Header>
<DocumentType>Order</DocumentType>
<PostingDate></PostingDate>
<OrderDate></OrderDate>
<BillToCustomerNo></BillToCustomerNo>

<Line>

<DocumentType>Order</DocumentType>

<Type>2</Type>
<ItemNo></ItemNo>
<DocumentNo></DocumentNo>
<Description></Description>

</line>

<Terms>14 days</Terms>

</Header>

</Root>

I have created same type of xmlport . is it work  or i need to be define DocNo for header and line label in xml document and xmlport.

thanks

surajit