Depends what you need, really. If your application doesn't have to be pretty, you can output the variables to the browser whenever they change, and view the page with a browser that doesn't require the entire page to load before displaying (I use an early version of NS). If your application does need to be pretty, and you don't want to save where you are in the process, reload the page, and and start where you left off, you could use frames and have one frame refresh every x seconds with a variable readout, while the other frame runs your app and updates the variables every so often.

More clarification on why you're trying to do what you're doing will help us explain the best way to do it.