Make new content appear on Submit

Hey guys

So, this is probably quite simple. I have a text feild that I need to have a phone number filled in. I then have the submit button below. When they click submit, I need a) the top text feild to be valid and b) content to appear below if its properly validated. Any ideas?

Hi AEI,

I'm not quite sure how that would work. What actually submits the form if the submit button shows new content?

Bob