How to stimulate MouseDown event (not click) in c#?

I 开发者_StackOverflowhave designed a GUI calc ,I have used flat buttons for the numbers, to get the button click feel I have changed the mouse down color, but when I use the numpad keys to do calc I am able to stimulate the click event. How do I stimulate MouseDown event?

Take the code that changes the button color from the mousedown event, refactor it into it's own method and call it from the keydown event as well.