Our study is on developing mathematics items for Computer-Based Testing (CBT) using Tablet PC. These items are subject-based items using interactive dynamic objects. The purpose of this study is to obtain some suggestions for further tasks drawing on field test results for developed items. First, we clarified the role of the interactive dynamic objects on each item, according to the problem-solving process. Then, we conducted the field tests with Japanese high school students. As a result, we identified possible improvements in item design. For example, we had some questions that cannot be asked in Paper-Based Testing (PBT), there is a possibility to evaluate the mathematical competencies more in detail according to the process, and so on. Here we shall show a few examples. Finally, we hope to make a contribution that might inform assessments and examinations to support progression between secondary school and tertiary education.