I built a dependency-driven scheduling engine entirely in Excel/VBA

Description and use

A team built ProjectEngine, an open‑source Excel/VBA engine that automatically calculates dates, critical paths, and more, enabling dependency‑driven scheduling in Excel without manual updates.

Problem

Teams needed credible project schedules but lacked access to Microsoft Project or Primavera P6; manual Excel Gantt charts required constant manual updates when tasks changed.

Outcome

Teams can maintain accurate, dependency‑driven schedules entirely within Excel, eliminating manual updates and reducing errors.

Workflow

• 1. Define tasks, durations, and dependencies in Excel sheets.
• 2. Run ProjectEngine VBA modules to read data into memory arrays and dictionaries.
• 3. Detect cycles and calculate tasks in topological order.
• 4. Compute finish‑to‑start, start‑to‑start, finish‑to‑finish, lag, milestones, and summary tasks.
• 5. Generate baseline, actual, and forecast dates and calculate critical path, longest path, total and free float.
• 6. Incrementally recalculate only affected tasks when changes occur.
• 7. Write updated dates back to Excel in batches and rebuild Gantt shapes efficiently.
• 8. Visualize results with interactive Gantt bars, dashboards, and S‑curves.

Evidence

ProjectEngine is an open‑source scheduling and project‑controls engine written entirely in Excel/VBA.

Source

Everything runs locally inside Excel. There is no installer, server, external account or cloud dependency.

Source