Building a Parametric Excel Spreadsheet (from scratch) for Easy Scenario Analysis

So, what is a parametric spreadsheet?
Valid question. In comparison to a static/base case/deterministic spreadsheet, a parametric spreadsheet is set up in such a way that key parameters and assumptions can be changed without invalidating the underlying calculations. So if you've found that your project is delayed by a year or that CAPEX is higher than anticipated -- you can incorporate these changes into your spreadsheet without breaking everything and instantly see how they affect value.