As part of a first-year college Introductory Physics course, I have students construct an Excel[R]: spreadsheet based on the differential equation for pendulum motion (we take a pendulum having a light bar rather than a string, so it can go "over the top"). In extensive discussions with the students, I find that forcing them to make the spreadsheet "themselves", entering velocities as position differences divided by time, etc., leads to a firmer grasp of basic calculus concepts. And, the instant graphical response of the finished product gives a sense of accomplishment as well as a lot of fun while building intuition about pendulum motion.