It's not Vb or C#, but I did write a similar GUI-based program in C++ using wxWidgets (works on Mac, Linux and Windows). It's called "firmata_test", and you can download it here:
http://www.firmata.org/wiki/Proposals
Scroll down and look for the screenshot on that page. Unfortunately, wxWidgets has a steep learning curve, but it's the only toolkit that produces native apps for all 3 platforms from the same source.