part of what makes Mathematica notebooks particularly powerful is that they are Mathematica expressions themselves (Mathematica expressions are M-expressions),

part of what makes Mathematica notebooks particularly powerful is that they are Mathematica expressions themselves (Mathematica expressions are M-expressions), thus they can be thoroughly manipulated in all sorts of ways. then there's Dynamic[1], which is the most straightforward event mechanism you're going to find in any language [1] http://reference.wolfram.com/mathematica/ref/Dynamic.html http://reference.wolfram.com/mathematica/ref/Dynamic.html