Is there a way to show a custom error message...

Is there a way to show a custom error message for an invalid column?

I’m guessing you mean for a data validation error. No. One thing you could do is provide input guidance in the column description. Eg: column name: Price, column description: enter a value between $1 and $99

You can always add a Show column right after the column in question, where you can display a message if the value entered is invalid. I do this several places in my app. Set the value for the content to show, and set ShowIf accordingly. Then use a format rule to display the content in red and bold - never fails to draw people’s attention :=)

Thanks for the suggestion.

In the invalid value error message box you can put a nested IF like
IF([value] > 99, “too high”, IF([value] < 1, “too smal”), x) .

The x just satisfies the IF statement and will never be used if your valid_if constraint states that [value] needs to be between 1 and 99. (I never bothered to learn the IFS statement ^^) This post is old so I don’t know what changed in appsheet since then but this way you can have different error messages.

AppSheet added custom error functionality in September 2018:

@Jonathon thank you for answering so many questions and helping out so many others in the community!

@Jonathon you’re da man!