multiple select list

Hello All, I have seen what I am trying to do on other web sites, but they were written in client side scripting languages. This may or may not be a limitation of server side scripting languages. What I am trying to do is dynamically generate 2 drop down list. I want the second list to contain different values based on what people choose in the first drop down list. If someone could guide me to some documentation on how to accomplish this it would be greatly appreciated. Thanks, Preston