creating dynamic form

Hi,

Does anyone know how to create a dynamic form in the 2.0 version? I have been looking through the discussion and help articles and can't seem to find any relevant articles that's not using the 1.0 forms.

I am trying to create a dynamic form that shows the next field depending on the payment method chosen. Eg credit card - billing contact name field appears, but if they choose invoice, this field doesn't show.

Can anyone help with this?

thanks.