I'm not sure if you already fixed this. However I believe I found a solution to your problem. If you look in the manual at the System Expression, there are Regular Expressions available. Regular Expressions allow you to search for matches in a string/text according to a pattern that you define such as a range from 0 to 3. In Regex, this range pattern would look like this: "[0-3]". For more information on Regular Expressions, I would advise going to the Mozilla Developers Network Javascript Guide which provided an excellent tutorial section on Regular Expression. I've attached a modified version of your .capx that will now display a message to the user when they press a button. The message will tell them if they entered a correct character or not. Hope this helps.