Hi Jade,

I want to be prompted
when a animal number is entered that already exists.


Use Data, validation for this.

- select the range that will get the numbers (lets say the entire
Column A)
- Choose Data, validation
- Click the dropdown box and select "Custom"
- enter this formula:
=COUNTIF(A1:$A$1,A1)<2

(notice the dollar signs!)

Regards,

Jan Karel Pieterse
Excel MVP
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