Enhance Estimator with Time Calculations

I already have a working estimating spreadsheet program with extensive data base. I now need to add further columns to improve the estimating spreadsheet.

Here is what I’m looking for:
• Add to the current spreadsheet with additional information i have.
• Display the information from a data base.
• Make sure the new calculations pick up the same input data fields
• Provide clear, concise documentation of every new function and a short change-log so I can track what was modified.
• Include a small sample project or test file showing the results of the new time calculations against known benchmarks; this will be the acceptance criterion.

The existing program is stable and I have full source control access; you will receive a Git branch to work in. Clean, well-commented code is essential because I will be maintaining the tool after this phase.