Duplicate Prevention: COUNTIF & COUNTIFS Rules
This lesson is part of the course
In this lesson
You build the rules that stop Larkspur from paying a supplier invoice twice: a count per invoice number, a supplier + number key, and an entry rule that blocks only the repeat.
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Lessons in this course
- Number & Date Rules as Check Formulas Locked
- List Rules: Allowed Values with COUNTIF & MATCH Locked
- Dependent Lists: Category → Item with INDEX/MATCH Locked
- Text Length & Pattern Checks: LEN, LEFT, SEARCH Locked
- Duplicate Prevention: COUNTIF & COUNTIFS Rules Locked
- Cross-Field Rules: End ≥ Start and Shares = 100% Locked
- Input Form with Error Messages & an Error Summary Locked
- Template Protection Checklist & Completeness Dashboard Locked