Numeric Data Validation Update

I have a Google Sheet that already holds important figures, but right now anyone can type anything into those cells. I want to tighten things up by adding new data-validation rules that accept only the numeric ranges or patterns I specify and reject everything else with a clear custom warning message. The job is solely about creating these new rules—no edits to existing ones or cleanup of bad entries is required. If you’re comfortable building validation logic directly in Google Sheets, including custom formulas where native options fall short, that’s exactly the expertise I need.