Rotate 90˚ Button??

Is there a button we can add to the toolbars up top to rotate an object 90˚ with each press? I thought there was but I can't find it now. Failing that, is there a macro someone has to add this feature? What about rigging a short-cut key to the button or macro? That would be perfect. I don't know how to write macros, and to me, it's all Greek.