Yes. This will require a few steps.
1. First you need to make a copy of a line 14, which is a validation for the name field and past it under line 20. And then you will need to update two things: the form element name, and the last parameter value from 1 to 7.
2. Then start by copying line 68 to 77 and pasting that under the form field you have added. Again make sure to replace the name with your form field name. If you have already applied spry validation, then you probably just need to surround the spry with line 68-72 and line 74-77.
Basically, if you use one of the already existed form elements as a starting point, and just change the form element name in the validation and add the extra line of code at the top of the page, you should be able to add server side validation to your new form element.