Excel Model Builder

Step 3: Build with Formulas

Rules for good models:

1. Inputs highlighted (yellow cells = editable)
2. No hardcoded numbers in formulas — reference the Assumptions tab
3. Clear labels for every row and column
4. Consistent formatting (currency, percentages, dates)
5. Error handling with IFERROR()
6. Named ranges for key assumptions

Step 4: Create the Spreadsheet

Use openpyxl (Python) to generate .xlsx files with:

• Multiple tabs
• Formulas (not just values)
• Conditional formatting
• Number formatting
• Headers and borders
• Print-ready layout

Output

Generate actual .xlsx file with:

• All formulas intact
• Formatting applied
• Sample data that can be replaced
• Instructions tab explaining how to use it

Quality Checklist

• All inputs on one tab (Assumptions)
• No hardcoded numbers in formulas
• Yellow highlighting on editable cells
• Dashboard shows key metrics at a glance
• Formulas use cell references (not typed values)
• Error handling on division formulas
• Instructions included