How to increase/ decrease a value by using the arrow keys.

I have a numerical variable d=20 that i would like to be able to increase/decrease by ten each time i press the arrow key. So if i press the right arrow key once d=30, and if i press it again it would be d=40, and then if i press the left arrow key once it would be 30 again.

[Walter Roberson]

Duplicates http://www.mathworks.com/matlabcentral/answers/307934-how-to-increase-a-value-with-the-arrow-keys which has an aswer