hlep wiht login form/xml..

Question

I am workign on a program and the only part i have left to complete it the login form.....
i have used an xml file to store my customer data like so...
<?xml version="1.0" encoding="utf-8" ?>
<Customers>
<Customer>
<FirstName>Jim</FirstName>
<LastName>Jones</LastName>
<Email>[email protected]</Email>
<Password>jjones</Password>
<IDnumber>1637</IDnumber>
<LoginID>1637</LoginID>
</Customer>
</Customers>

i want to have the user type in his username in usernametextbox.text and password in passwordtextbox.text then have the program search throu the xml file for a match loginID (username) and password....if no match is found show error message, and if a match is found frmcustomermaintenance.show

i know im prolly gonna ahve to use selectsinglenode or something like that ....but ive eben tryin and its not working, i dont have much experience using xml fiels so if someone could help me out it would be much appreciated.
thanks
MILT