I need something to add line in xml

I need something to add line in xml

i need big help in xml file. I need to know how to add a new line in all
my <Invoice> </ Invoice>. for example:
<Invoice>
<InvoiceNo>FR 2013A/5391</InvoiceNo>
**<DocumentStatus>**
<InvoiceStatus>N</InvoiceStatus>
<InvoiceStatusDate>2013-07-01T09:00:25</InvoiceStatusDate>
<SourceID>Admin</SourceID>
<SourceBilling>P</SourceBilling>
**</DocumentStatus>**
</Invoice>
so i need to know how can i add <DocumentStatus> after
<InvoiceNO></InvoiceNO>, and </DocumentStatus> after
<SourceBilling></SourceBilling> ? The values inside off
<InvoiceNO></InvoiceNO> and <SourceBilling></SourceBilling> comes from DB,
so in other <Invoice></Invoice> that values comes diferente. Thats my big
problem. I need file to do this operation, can anyone help me?