passing first name, last name, phone no from a form to lightbox

I have a contact us form where I am collecting the First Name, Last Name & Phone number of the student and then submit button which saves this information in contacts, but immediately I want to open a lightbox where more details are asked to students to fill.

I want all 3 fields to be passed to the lightbox so I can use them and store them as well in contacts.

How do I do this in velo?