Hi JADarnell,
It all depends on what you're asking, exactly. When you say you want to open another dialog when the user selects a radio button, we need to know how you're creating the dialog in the first place. There are two main ways to do this--1.) using InDesign's built-in dialog object, or 2.) using ScriptUI, which is an ExtendScript object. How can you tell which is which? If you're using app.dialogs.add() to create the dialog box, you're using the InDesign object; if you're not, you're using ScriptUI.
If you're using the InDesign dialog object (in the ESTK, open the Object Model Viewer, then select the InDesign DOM corresponding to your version of InDesign), then you can't really do this without closing the original dialog box--all InDesign dialogs are modal. While you can, apparently, attach event listeners to the InDesign dialog object, I've never done it for precisely this reason. I'll take a look as soon as I get a few minutes.
If you're using ScriptUI (in the ESTK, open the Object Model Viewer, then select the ScriptUI DOM), refer to the "User Interface Tools" section of the JavaScript Tools Guide (in the ESTK, choose Help>JavaScript Tools Guide to display this PDF). The reference section on the radiobutton control refers to an onClick event and to a notify() method. Unfortunately, most of the ScriptUI examples use resource strings to define dialog boxes, which is, in my opinion, the worst way to do it--but you can still search the SDK examples (they're in the Samples folder inside the SDK folder in the folder containing the ESTK application) for "onClick" to see some examples.
Thanks,
Ole