Typing mathematics is sometimes difficult with text editors for students with motor impairment and other associated impairments. The HandiMathKey is an application co-designed by mathematics teachers and occupational therapist. In this paper we report an mixed evaluation based on the UTAUT theoretical framework. We used questionnaire and interview to understand professional’s usage of HandiMathkey. This study shows how the questionnaire and the interview complement each other, and how the two professionals can take a complementary approach to understanding the use and new needs of HandiMathkey as part of a user-centred design approach.