If you can't beat windows calculator, why not use it? My app shells out to the windows calculator, sends key presses, copies the result to the clipboard and displays that result. **NOTE** Like any good WTF code, there are some side effects. Whatever is in the windows clipboard will be overwritten. I'm sending an alt-F4 keypress to close the windows calculator, so if things don't go quite right then something else is getting closed (hope you saved!).