In view of the importance of reliable duration measures for bond immunization strategies, this paper considers, from a pedagogic perspective, the duration concept. Both a basic bond model and a more realistic bond model, which accounts for the accrued interest, are considered. The use of graphical features and scroll bars in Microsoft Excel^TM allows the duration concept to be delivered via an interactive approach. This paper also addresses an unresolved issue on bond duration. Specically, it explains why a saw-toothed time pattern of traditionally-defined duration exists and provides a corrective measure, which is easy to implement on Excel. Analytical materials pertaining to bond duration, as well as illustrative examples based on actual bond quotation data, are provided.