How to create dynamic data when I click on a link

I need to know the easiest way to create dynamic data when you click on a link, and also I need to know how to make checkbox options come up depending on what you choose in a drop down menu. I'm not sure if this has to be database driven, or JavaScript, or something else. I hope someone can help me soon, I will gladly offer my help with whatever I can!! I am in the process of a website redesign (it's almost finalized) and I have run into a stumbling block. It's a site where people can register for conferences, and there may be anywhere from 2-6 conferences up on the site at one time. Right now, there is a generic register page that a user needs to choose the conference they want and then they have to remember which options they wanted for that particular conference. What I want to happen is: when a person comes from a particular conference to that register page, I want that conference name to be there with the appropriate options/info there for them to check off. I also need that same register page to display the correct options depending on the conference someone chooses. I hope that all makes sense!