Write XML nodes to file

Question

Hi,

Has anyone come acroos this scenario
I have a XML file of the following structure        

<Customers>
        <Customer>
                <FirstName></FirstName>
                <LastName></LastName>
        </Customer>
        <Customer>
                <FirstName></FirstName>
                <LastName></LastName>
        </Customer>
</Customers>

Now i need to append a  "Customer" tag programatically to the XML file. I was able to add <Customer></Customer> using appendchild() to the root tag. But it did not write the children "firstname" and "lastname".What is a better way that will add the entire Customers tag block including firstname and lastname