you can't do it because page is actually refreshing and row is added client side so when validation done then you will redirected to same page with validation errors you will not see dynamically added dom because as i said it was happend client side not in your code...so all you can do is use session
and then at load time manually validate and add them to page.
Using SESSION
might not be good idea because for that you will have to code more complex helpers and validation methods and etc...
Other possible solution
use
jQuery.validate
plugin that allow us to validate dynamically added rows ( fields , dom ).take benefit of mysql and add those field into database with possible error stored in db and send it to view file.