Can I make a submit button from one form also submit a second form's info?

Yeah... that architecture doesn't work too well because you have to remember a bunch of values between one form and the next: a better way is to have one big form with everything in it, and use Javascript to hide and show bits of the form depending on what you press on the top (so instead of being submit buttons, the scripts kick off javascript functions to show and hide the elements). Check out my site: http://www.opwernby.com/ -- press "log in" and you'll see what I mean: the form has tabs on it that you can press, but in reality, it's not submitting anything when the tabs change. If you do "View Source" on my site, you can see the script files involved: feel free to download them all.

If you have to remember values between pages, then you're going to have to replicate every field on every form as hidden fields on the other forms, then set the values accordingly every time each form loads -- this is another way to do it ( <input type="hidden"> ) -- assuming you have some kind of backend scripting language like ASP or PHP, that's not too hard to do.