A lot goes into this. How big is the ball, is air resistance going to be a factor, is the ball spinning, how heavy is the ball, what velocity is it being projected at, how far must it go before it hits the wall? One thing you could do is just shoot the ball about 10 times and mark where the ball hit and then adjust the laser to point there. If you are looking at predictive power with a changing setup you will of course need to develop a physical model. Look into books on computational physics for this. Obviously gravity is your dominant force here, so the standard equations of one-dimensional motion might do just fine, but if these other effects are large then a more complex model will have to be devised.
Anonymous Coward writes: "Quarked.org is a website from the University of Kansas that attempts to counter the dogma which states that physics and other abstract concepts can not be taught to younger children in school. The site takes a neat approach to introducing sub-atomic particles as characters in a cartoon along with several flash based games in order present a selection of concepts previously thought only understandable to students in college. Early results seem to indicate that the children actually develop an understanding of the ideas presented on the website and though outreach programs. The idea is to introduce cool science content to children early enough to reduce the overwhelming pressure that physics or other technical classes are too difficult. More high school kids enjoying science, what a cool and neat concept!"