The process of activity scheduling is crucial to the understanding of travel behavior changes. In-depth research is urgently needed to unearth this process. To reveal this process, a new computer program, REACT!, has been developed to collect household activity scheduling data. The program is implemented as a stand-alone program with Internet connectivity for remote data transmission. It also contains a GIS for location identification and a special feature that traces the decisions in scheduling process. A pilot study was conducted in Irvine, California to evaluate the program performance. Experience from the pilot study validated the program's capability of guiding participants to complete data entry tasks on their own, thus the objective of reducing the cost and human resource of such a computerized survey is achieved. Other positive results regarding objectives of reducing instrumental biases and expanding program capabilities were also obtained. Areas for improvement were also identified. Based on the pilot data, activities with shorter duration were found more likely to be opportunistically filled in a schedule already anchored by their longer duration counterparts. In addition, the situations (e.g., location, involved person, and day of the week) under which an activity occurred were found related to its scheduling horizon. Analyses were also performed to validate that the above findings hold in the presence of a third factor (i.e., in-home vs. out-of-home, and work/school vs. non-work/school). Additionally, analysis of tour structure reveals that a certain portion of trip-chains was formed opportunistically. The proportion of opportunistic stops tends to increase as stop sequence increase. Travel time required to reach an activity is also positively related to scheduling horizon of the activity, with distant stop being planned earlier.