Force user to make a radiobutton selection?

That's a tough one because once the form is open the user can navigate to any location. But you could hide the entire form except for the Radio Buttons until the user selects one. Do this by placing all the other fields in one or more subforms that you can easily hide/show from a script. There's also a fancy way to give the other form fields a disabled look until one of the buttons is selected. But it will take more coding. Here's an article:

http://www.acrobatusers.com/tutorials/2007/09/js_disabling_fields

Thom Parker
The source for PDF Scripting Info
[url=http://www.pdfScripting.com]pdfscripting.com[/url]

The Acrobat JavaScript Reference, Use it Early and Often
[url=http://www.adobe.com/devnet/acrobat/javascript.php]http://www.adobe.com/devnet/acrobat/javascript.php[/url]

Then most important JavaScript Development tool in Acrobat
[url=http://www.pdfscripting.com/public/34.cfm#JSIntro][b]The Console Window (Video tutorial)[/b][/url]
[url=http://www.acrobatusers.com/tutorials/2006/javascript_console][b]The Console Window(article)[/b][/url]

Thank you, Thom. The 'hide the rest of it' route is definitely the way to go in this case.