I need a lightweight Windows desktop program that runs entirely offline and helps me analyse buy-sell opportunities inside a single Excel sheet of up to 10,000 rows. The workflow is straightforward: I upload an .xlsx file (or paste / type data manually when that is quicker), pick the Circle and Denomination I’m interested in, and the application should immediately show me: • the best purchase rate once commissions are deducted • the best sale rate • the gross margin between the two • a ranked list of every possible buy-sell combination A clean, uncluttered graphical interface is essential; I want a single-window layout with clearly labelled controls so a first-time user can finish the task without reading a manual. When the analysis is done, the user must be able to save the filtered and ranked results back to Excel with one click—no CSV, no PDF, just a native .xlsx file. Deliverables • Compiled Windows executable that works without an internet connection • Fully commented source code so I can maintain or extend it later • Brief read-me or inline help describing the required column headings and any setup steps Acceptance criteria The program processes a 10,000-row sheet in under 10 seconds on a typical office PC, saves an accurate results file in Excel format, and displays all calculations correctly when tested with several sample datasets. If you have questions about edge-case handling or preferred libraries, let me know and we can lock down the details before you start coding.