Need form validation in Virtuemart/Joomla

Dear developer, I have two fields which are to be required in the checkout of my Virtuemart/Joomla shop. One is the TOS checkbox (Terms of Service) and the other is an input field where the client must enter a name. I have attached the php file with the form code. It is located in the template\html\com_virtuemart\cart override folder of the site. The file is [login to view URL], please find it attached to this post. There are small changes from the original Virtuemart file and the changes are well commented in code. Please ask if there are questions. I think this might be a simple task for an experienced programmer. You will get access to the full site and a full webserver control panel at Hostgator to fix this issue. It is a development copy, not the production site. Thanks!