Women are underrepresented in the field of Computer Science. This project aims to help Secondary School girls develop an insight into the role computers play in society and to learn some of the key skills in computing including computer programming. Exposure to Computer Science, in home or school environments, and encouragement from family and peers are leading factors that influence girls' decisions to pursue careers in Computer Science. Other factors include the girls' perception of their own problem solving ability, an understanding of the diverse applications of Computer Science and related career paths and the potential for positive social impact. This paper describes the design of an after school computing programme, CodePlus, which uses a novel 21st Century learning model. Pre and post questionnaire are being used to explore girls intentions to study CS, their confidence to study CS, perception of CS as a career, gender perception of CS and IT profession and self-efficacy following participation in the CodePlus programme. Preliminary results comparing pre questionnaire results with a male control group highlight differences in how girls see themselves in terms of CS capabilities and their future potential. Initial post questionnaire findings show a significant increase in the participants' perceived programming ability.