Real-time programmers have to deal with the problem of relating timing constraints associated with source code lines to sequences of machine instructions. This paper describes an interface that was developed to assist users in this task. Portions of programs can be quickly selected and the corresponding bounded times, source code lines, and machine instructions are automatically displayed. In addition, users are restricted to only selecting portions of the program for which timing bounds can be obtained. The result is a user-friendly interface that assists programmers in the analysis of timing constraints within a program.