Hi Daniel (and Larry), I’ve got two ideas: 1. Monitor Total Slack for the task you are changing. I know this is obvious, but as long as your deliverables and completion milestones are suitably constrained, you can be assured that a positive value for Total Slack (after your change) implies no impact on the critical path. 2. If you are trying to shorten the project by attacking the critical path (or paths) directly, then parallel (near critical) paths can limit the impact of your changes. It’s difficult to predict in advance where the “critical path” will jump to without visual inspection, but you can anticipate these by computing and displaying Drag. Drag is the maximum amount of time that may be shaved from the project schedule by shortening the duration of a specific task. There is a macro to compute it . The default calculation is based on the overall project completion, but you can tailor it to specific deliverables if needed.