With the spread of computers and networks into schools, it becomes more and more important to make them useful for education. We are currently working on the project of holding Squeak workshops in schools. In these workshops, students try to make their original works, but there is no method to see the building process of their works and share their ideas. In this paper, we propose an action history model for managing user operations on SqueakToys. In the model, the object manipulation events for the SqueakToys application level are captured and stored with the associations to mouse and keyboard events for the operating system level, so that we can focus on the important part of the building process. We have also designed the playback function of action histories at varying speed, as a visualization of action histories. In addition, analysis on the action histories and its utilization are discussed.