Using DIV tags to hide form sections until Button OnClick

Hi All:
I have a lengthly form that I have crated in ASPPro 5.1.
It is comprised of two sections.
In the Add.asp form I have two buttons, one for section 1 and one for secton 2, so when onclick they will each envoke a separate function to allow those sections to appear to the user using DIV tags I hope.
My problem is, I don't know where to place the DIV and /DIV tags? Since the Add.asp page has no HTML, I can't figure out what file or where I need to place these tags. Also, where do I need to place the function? In the Add.asp page?
Any help would be great..