Numeric VLOOKUP & Duplicate Flags

I'm seeking an Excel expert for a precision task on a static dataset.

Requirements:
- Use VLOOKUP to find numeric values.
- Implement a method to flag duplicates for manual review.
- Ensure the function is set for a one-time analysis.

Ideal Skills:
- Proficiency with Excel formulas, specifically VLOOKUP.
- Experience with handling duplicates in datasets.
- Strong attention to detail.

Looking for a quick, accurate, and efficient solution!