Welcome, but pl take a moment to go back and press the YES buttons (like the
ones below, from where you're posting) in ALL responses which helped.
Yes, but its not foolproof since dates are just numbers in Excel,
so any number in col B would also satisfy ISNUMBER
Your formula above could be simplified to just:
One other way, more robust, is to validate/trap it for a certain date range,
eg: between 1 Jul 2008 to 30 Jun 2009:
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