This document describes an expert algorithm implementation for Automated Valuation Models (AVM) to help real estate appraisers value properties. The algorithm collects property characteristics and sale prices from online listings to find comparable properties in a similar way to a human appraiser. It uses an modified inverse distance weighting estimator to determine a property's value based on comparable properties found. The algorithm is implemented using R and Shiny to allow configuration of rules and provide an interactive interface for appraisers to explore estimation results. Ongoing work aims to improve precision through machine learning and geostatistics models.