Outcome-Based Education (OBE) has become an essential framework for engineering education under the National Board of Accreditation (NBA). Criterion 3 of NBA focuses on the evaluation and attainment of Program Outcomes (POs) through measurable and transparent processes. This paper presents a structured and practical methodology for calculating CO and PO attainment using an Excel-based automated tool. The methodology integrates both direct and indirect assessment techniques and provides a systematic approach for data collection, analysis, and interpretation. A case study from a Mechanical Engineering course is included to demonstrate real implementation.\\n\\n