Contact Form 7 – Custom Validation

I need to validate just one field (called ‘Instance’) to accept lowercase ASCII letters and numbers only, the first character also has to be a letter not a number. It will accept uppercase characters but we will need it to lowercase them on input. So if someone uses the instance name McDonalds it will be lowercased to mcdonalds (not just with CSS). Spaces are not allowed either.

Is this possible with CF7? If so please explain how.

I’ve already tried this custom validation method but even with the preset custom validation in the file it was just displaying the field shortcode rather than the field itself.

Thanks

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