This paper deals with errors in using spreadsheets and analysis of automatic recording of user interaction with spreadsheets. After a review of literature devoted to spreadsheet errors, we advocate the importance of going from error detection to interaction behaviour analysis. We explain how we analyze screen captures and give the main results we have obtained using this specific methodology with secondary school students (N=24). Transcription provides general characteristics: time, sequence of performed tasks, unsuccessful attempts and user preferences. Analysis reveals preferred modes of actions (toolbar buttons or menu commands), ways of writing formulas, and typical approaches in searching for solutions. Time, rhythm and density appear to be promising indicators. We think such an approach (to analyze screen captures) could be used with more advanced spreadsheet users.