Psychroisis, a term coined to describe the intricate relationships between thermal and psychrometric factors, plays a crucial role in various engineering and environmental applications. The analysis of psychroisis requires a deep understanding of thermodynamic principles, psychrometric charts, and computational tools. In recent years, the use of spreadsheet software, such as Microsoft Excel, has become increasingly popular for engineering calculations and simulations. This paper presents the development of a ThermExcel programme for psychroisis, which leverages the capabilities of Excel and VBA to create a comprehensive tool for thermal and psychrometric analysis.