The quantification of a decision maker's judgements about uncertainty is a key step in Bayesian analysis of a decision problem. This paper is concerned with the use of an on-line computer system to assist a person in quantifying his judgements, with reference to reliability problems. A computer program is designed to display a questionnaire on a console, and to allow the user to interact with the computer during his course of quantification. This interactive feature provides an assistance for the user in removing inconsistencies of his responses to the questionnaire. Furthermore, the responses to the questionnaire are processed in real time to fit a smoothed cumulative distribution to facilitate the user's subsequent analysis.