creating a graphic interface

I am using an L293D motor driver to steer two DC motors on an Arduino Decimila. Everything is going fine, it is working.
The next step is to create a graphic interface (two sliders) that let me control the motors. The only problem is that I have absolutely no idea how to do this. I know that I can use processing to visualize the incoming data, but I don't know if there is a way to create a graphical interface that can be used as an input.

Does anyone know this?

Try to look at the ControlP5 library for processing, really easy to use for creating GUIs.
Or you can use Flash to make your GUI and send the value to the Arduino.