How do I add an additional amount field?

Hi there,
I have a fixed amount field ($325) for the first child and any additional child will cost $295. How would I do that?
svenskaskolanwashingtondc.org/new/index....an/register-age-4-18

On another note, how do I make the height of the form fields larger?

Thanks in advance. Love your components. Henrik

I moved my questions into the ticket support area. Henrik