Yes your experiment is possible. If all you need is the cued and uncued times its easy. Users can run an online applet demo provided by [psytoolkit][1]. You can embed the applet in a survey where users can record their times. For more in detail data analysis I recommend that you roll your own based on psytoolkits model. Given how simple the experiment is even starting from scratch should be easy for a computer science undergrad with some experience in .net or another web language. [1]: http://psytoolkit.gla.ac.uk/library/ior/