Desktop Address Proximity Finder

I often receive two separate address databases: one is my “master” list of origin points and the other is a pool of candidate locations. On Windows I’d like a small, self-contained desktop utility that lets me:

• import each list from CSV or Excel
• have the app automatically geocode every address (Google Maps, Bing, OpenStreetMap or similar—whatever keeps key usage limits manageable)
• calculate straight-line or road-distance metrics and, for every record in List 1, return the five closest matches from List 2
• export the combined results to a new CSV/Excel file with the original fields plus the five nearest locations and their distances

A clean interface with drag-and-drop or “Browse…” file selection is plenty; no multi-user features are required because the tool will live on my own PC only. Performance should stay reasonable with at least 10 000 rows per file, and the executable should run on Windows 10/11 without needing me to install full development environments—bundled runtimes or a simple installer are fine.

Please build in a way that lets me enter my own API key for the mapping service and tweak distance units (miles or kilometres). I’m open to .NET, Python with an embedded GUI, or any technology that compiles to a straightforward Windows installer. Once delivered I’ll test with sample files; acceptance is a correctly generated output file where the five-nearest logic matches manual spot checks.

I have attached 2 files for your review (I have already geocoded these lists). I would like to find the 5 nearest ALF Facilities to each law office.

Thanks