Notes/Domino 4 and 5 Forum

I need to create a look up kind of functionality on the web
I have a field and button. When a user enters a userid in the field and hits the button. The button should go to a view and search documents by key (the value in the field) and then populate the other three fields with Name, email and Department information.
can I just write a Lotus Script in the button or Do I have to write a an agent and call it in the button. Does anybody have a sample code?
Thanks,