A prototype cost estimating tool was built using an iterative design approach to help training managers assess the impact of changes in the training environment on course life cycle costs. In the first of two evaluations, training managers evaluated the prototype tools during a demonstration for both functionality and face validity in their environment. They also evaluated the usefulness of different levels of graphics and detail in a guide designed to assist the user with the tool. Feedback from the first evaluation was used to revise the prototype tool, and the guide usefulness ratings were used to select the guide for use in the second evaluation. The impact of the guide on performance with the tool was analyzed in a second evaluation. The second evaluation analyzed the difference in performance of two groups. The first group only had the users manual to help them solve the problems. The second group had the users manual and a performance aid to help them. Subjects' performance was compared on the number of spreadsheets used, number of errors made, and the amount of time they took to complete the tasks. The two groups did not significantly differ on these measures. / Ph. D.