Google Sheets Custom Function Development

I’m looking for someone who can extend Google Sheets beyond its native capabilities by writing custom formulas and functions through Apps Script. The core of the job is to take the logic I’ll supply, translate it into clean, well-documented JavaScript, and wire it seamlessly into a working spreadsheet. If a lightweight HTML sidebar or dialog is the best way to surface settings or results, feel free to include it—just keep the interface simple and responsive.

What I need from you:
• Robust, reusable Apps Script code that installs as one or more custom functions.
• A copy of the spreadsheet (or a blank template) with the script already bound and demonstrably working.
• Brief inline comments plus a short read-me so I can maintain or extend the solution after delivery.

Timeline: everything wrapped up and ready for hand-off within a month. To help me choose quickly, please point me to a few examples of past work where you’ve built similar formulas, automations, or front-end elements inside Google Sheets.