You can link the action 'Jump to slide X' to the radio button X. You have to be aware that at the end of the X-series of slides, you will have to direct to perhaps an 'end slide' p.e. by linking a similar action 'Jump to End slide' to the End of the last slide of the X-slides. Same for the Y-button, Z-button, etc.
To have a visual idea of the linking, you can switch to the Branching View.
Another approach is to make 4 movies. In the first you make the slide with the radio buttons, link the action 'Open project X' to X-button, etc.
Just a tip: can you mention the version of CP when posting a question on this forum?
As for tutorials, check the Adobe team blog: blogs.adobe.com/captivate or the blog of R Jacquez (both are mentioned in the main page of this forum). Have a look perhaps at http://blogs.adobe.com/captivate/2009/03/roundup_of_captivate_events.html
I have set up three buttons that branch as you suggested. This works fine for my first attempt.
I was trying to locate an object that displayed a defined number of radio buttons and then branched from the one chosen. I have not been successful yet; however, I will keep experimenting.
I am using the trial of Captivate 4 as a precursor to buying the e-Learning Suite. I just wanted to make sure it would do a few of the things I needed first.
Thanks again for your input.