On Windows 7 my regional settings use Lithuanian format thus the decimal symbol is , (comma), but I'm using EN keyboard layout and US language most of the time which uses . (dot) as a decimal symbol. And calcy doesn't honor that.
Because of this I can't use keypad with calcy as it's expecting , for a decimal symbol but keypad inputs . because of EN layout.
Try my plugin, it is a calculator that has these features you are looking for. http://sourceforge.net/projects/mathyresurected