Adding a row to a message

I have to add a row to an XML message.  The message has been modified through a For Each loop during which a property value has been accumulated from a value from specific child elements in each node.  After completing the For Each loop I need to create a node on the message to contain the same child elements as the rest of the message using the data accumlated in the For Each loop. 

 The message was origianlly created from a .CSV file.  It will publish to a database table through an XSLT. 

How do I add an additional row node to an XML message.