Sizing question on iFraming

I have a two page offer that I want to put in an iFrame. The section I want to frame on the first page is smaller in size than the section I want to frame on the second page. Once the info is input on the first page and a click is made to go to page two, the frame is smaller than the section of the page I need to show.
How can I get the second page iFrame to show more than the first page?