Use Data validation

Select column D

data=Validation

Select custom from the Allow: dropdown

put in the custom formula:

=CountA(D:D)<=13

then go to the message tab and enter your message

Change 13 to 12 if you don't have a header entry in D1.

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Regards,
Tom Ogilvy

"Gary" wrote in message
...
I have a sheet with Products on them. I only the customer to choose up to
12 items. They do this by putting a quantity in column "D".

I would like a message box to appear if they have filled in more than 12
rows for column "D". So on the 13th entry, the message box should appear.
How can I do this?

Thanks,

Gary